Paraspinal neuromuscular syndromes …

Neuromuscular Disorders

Updated 02.02.2026
Released 12.09.2002
Expires For CME 02.02.2029

Paraspinal neuromuscular syndromes

Authors: Pritikanta Paul MD, Elie Naddaf MD

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Editor: Nicholas E Johnson MD MSCI FAAN

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Paraspinal neuromuscular syndromes

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Introduction

Overview

Paraspinal neuromuscular syndromes describe a distinctive clinical presentation characterized by preferential or early involvement of the paraspinal or axial muscles resulting in a change in posture. These syndromes include dropped head syndrome, when weakness predominantly affects neck extensors, and bent spine syndrome or camptocormia due to muscle weakness in the thoracolumbar region, in addition to rigid spine syndrome. Although rare, this pattern is increasingly recognized in association with neuromuscular diagnoses but is unfortunately frequently overlooked on routine examination. Detection of this distinctive pattern is critical to help with diagnosis and initiating treatment in a timely manner where applicable.

Key points

	• Paraspinal neuromuscular syndromes describe a distinctive clinical presentation characterized by preferential or early involvement of the paraspinal or axial muscles resulting in a change in posture.
	• Recognition evolved from clinical observation of characteristic postural abnormalities, including dropped head syndrome (cervical extensor weakness), camptocormia/bent spine syndrome (thoracolumbar flexion), and rigid spine syndrome (paraspinal contractures with reduced spinal mobility).

Historical note and terminology

Recognition of paraspinal neuromuscular syndromes has evolved largely from careful clinical observation of characteristic postural abnormalities rather than from early etiologic classification. Lange and colleagues described severe neck extensor weakness using the term “floppy head syndrome,” most often in association with generalized neuromuscular disorders, such as myasthenia gravis, polymyositis, or motor neuron disease, though some cases lacked a clear etiology (56). Subsequently, dropped head syndrome was reported in patients with a noninflammatory myopathy predominantly affecting cervical and upper thoracic paraspinal muscles, often with only mild limb involvement (Suarez and Kelly 1992). Isolated neck extensor myopathy was later used as a term to describe a more focal disorder with a relatively benign course (49).

Bent spine syndrome or camptocormia (“kamptos” meaning “to bend” and “kormos” meaning “trunk”), often used interchangeably, is described as a forward flexion of the spine that worsens with standing or walking but resolves in the supine position (03). Camptocormia was long misidentified as a psychogenic conversion disorder, a perception rooted in its observation among soldiers during World War I (100). Gradually, the medical understanding of camptocormia shifted towards recognizing it as a physical manifestation of underlying neurologic disorders—both central, such as Parkinson disease (24; 35) and multisystem atrophy (115), as well as peripheral nervous system disorders like amyotrophic lateral sclerosis (128) and myopathy (58). Camptocormia became increasingly recognized as a myopathy presentation (57). Building on the same concept, dropped head syndrome and bent spine syndrome are being proposed as phenotypic expressions of a primary tardive myopathy predominantly affecting axial musculature (83).

In parallel, recognition of rigid spine syndrome contributed substantially to the understanding of axial neuromuscular disease. The term was used to describe a myopathic condition characterized by early and prominent paraspinal contractures resulting in markedly reduced spinal flexion and rotation, distinguishing it from the muscular dystrophies recognized at the time (27). This further evolved into a clinical description of a subset of congenital muscular dystrophies, often with early respiratory insufficiency (73; 34).

When a patient is presenting with muscle weakness predominantly affecting axial muscles, the presentation is referred to as an axial myopathy. Although the term “paraspinal” and “axial” are sometimes interchangeably used, paraspinal muscles are a subgroup of axial muscles that are adjacent to the vertebral column. Axial muscles include other muscle groups that play a role in trunk stabilization and posture maintenance, such as the splenius capitis.

Clinical manifestations

Presentation and course

	• Paraspinal neuromuscular disorders present with progressive weakness predominantly affecting cervical or thoracolumbar extensor muscles.
	• Common symptoms include axial fatigability, postural instability, pain, and a sensation of being “pulled forward,” which typically worsen with standing or walking and improve when supine.
	• The course is often slowly progressive, with early selective axial involvement that may later lead to fixed deformity and functional impairment.

Axial weakness commonly presents with difficulty maintaining an upright posture or keeping the head erect (61). Patients frequently report associated symptoms of muscle fatigue, axial pain, or a sensation of "pulling forward" that is often worse with prolonged standing or walking. Depending on the severity, patients may be unable to maintain their head up at a 45-degree angle while in a supine position. Paraspinal muscle atrophy and compensatory activation of hip extensors are other common physical findings. Other nearby nonaxial muscles, such as abdominal, pectoralis, or periscapular muscles, are commonly affected. The presentation may often be misattributed to degenerative spine disease. Distinct postural phenotypes map to different patterns of muscle involvement and underlying disease associations.

Dropped head syndrome is characterized by an inability to maintain head erect position due to muscle weakness or dystonia (104). When from muscle weakness, it may be caused by a myopathy, neuromuscular transmission defect, or a motor neuron disorder. Peripheral nerve disorders rarely present with dropped head syndrome. Physical examination may help determine the underlying mechanism, including assessment for fatigability with sustained or repetitive movements, signs of upper or lower motor neuron involvement, such as fasciculations or pathologic reflexes, or a myopathic pattern of weakness. In neuromuscular disorders, dropped head syndrome results from true weakness of the neck extensor muscles and usually improves or corrects when the patient lies supine as gravitational forces are removed. In contrast, head drop due to central nervous system disorders is caused by sustained dystonic or excessive activation of the neck flexors and may persist despite assuming a supine position.

Camptocormia is defined by marked forward flexion of the thoracolumbar spine that resolves when supine. Similar to dropped head syndrome, camptocormia can be seen in various neuromuscular disorders (61; 02; 122). Patients with spine deformities, such as severe scoliosis, may also have a “bent spine.” This can be challenging to differentiate, especially as scoliosis can be a comorbidity seen in patients with longstanding neuromuscular weakness.

Rigid spine syndrome, which often presents in childhood or early adulthood, features early limitation of spinal flexion and extension with relatively mild limb weakness and is frequently linked to inherited myopathies (eg, SEPN1-related myopathy) (34; 54; 123; 30). Progressive axial weakness with reduced spinal mobility leads to fixed hyperextension of the cervical, thoracic, or lumbar spine. On examination, neck flexion and rotation are markedly restricted, and forward bending is limited. This may be frequently accompanied by neuromuscular respiratory impairment. When rigid spine features are acquired, alternative etiologies should be considered, including central nervous system disorders, such as stiff person syndrome, inflammatory or degenerative arthropathies (eg, ankylosing spondylitis), and structural or iatrogenic causes, such as prior spinal fusion.

The disease course is usually variable and depends on the underlying cause. A subacute or rapidly progressive course raises suspicion for an underlying immune mediated or toxic process. In contrast, genetic forms typically follow a slowly progressive course over years.

Prognosis and complications

The prognosis is highly heterogeneous and primarily determined by the specific postural phenotype, underlying etiology, and age at onset (98; 122). Immune-mediated or drug-induced disorders may respond well to immunotherapy or withdrawing the offending drug, respectively (02). The extent of improvement varies ranging from halting progression to complete resolution of the condition. Genetic forms of axial myopathy typically follow a slowly progressive course with limited treatment options and variable long-term outcomes (34; 70). Neurodegenerative disorders, such as amyotrophic lateral sclerosis, have the poorest progression (39; 79). In a study, dropped head syndrome occurred in approximately 1.3% of patients with amyotrophic lateral sclerosis and usually appeared as an early feature within the first 1 to 2 years after onset. In another study, neck weakness was a potent independent prognostic factor in amyotrophic lateral sclerosis: the Medical Research Council (MRC) score for neck flexors was the most significant prognostic factor for survival, loss of speech, and loss of swallowing function and was also a significant prognostic factor for loss of upper limb function, difficulty turning in bed, and loss of walking ability (39). Although median survival for amyotrophic lateral sclerosis is 2 to 4 years, there is broad variability influenced by clinical features, such as age at onset, site of onset, and presence of other comorbidities (40).

Common complications of axial myopathy include chronic pain, postural deformity, falls, functional dependence, and reduced quality of life (135; 98; 122). Bulbar muscles are commonly affected due to their proximity (02), causing dysphagia, particularly with dropped head syndrome, and can lead to considerable weight loss, aspiration, and pneumonia (122). Progressive spinal deformity and skeletal complications are also common in axial myopathy (34). In rigid spine syndrome particularly, early spinal rigidity is associated with early scoliosis, and after initial improvement, skeletal deformities supervene (34).

Respiratory insufficiency is a characteristic and potentially life-threatening complication of axial myopathy, particularly in rigid spine syndrome (34; 61; 70). Patients often have a restrictive pattern on pulmonary function testing that can be due to weakening of the diaphragm and other respiratory muscles, or due to mechanical restriction with spine deformity or rigidity. Respiratory involvement typically manifests with sleep-related disordered breathing symptoms and may require noninvasive ventilation during sleep. The combination of spine rigidity and respiratory insufficiency contributes significantly to morbidity and mortality in these patients (136).

Biological basis

Etiology and pathogenesis

	• Muscle diseases are a common cause of paraspinal neuromuscular syndromes, with motor neuron diseases and neuromuscular junction disorders also plausible causes.
	• Several treatable conditions must be identified early, including inflammatory myopathies, sporadic late-onset nemaline myopathy, myasthenia gravis, and drug-induced myopathies.
	• Genetic causes span structural muscle diseases (facioscapulohumeral muscular dystrophy, LMNA-related myopathies, RYR1-related myopathy, myofibrillar myopathies) and metabolic myopathies (Pompe disease, lipid storage myopathy, mitochondrial myopathy).

Paraspinal muscles are often susceptible to neuromuscular disease and represent an under-recognized feature of muscle disorders, with imaging-based studies demonstrating their frequent and prominent involvement across a wide range of myopathies. Axial musculature involvement occurs in the majority of myopathies when paraspinal musculature is examined (135). Even in diseases named after a certain pattern of nonaxial muscle affection, such as facioscapulohumeral and limb girdle muscular dystrophies, affection of the axial musculature is often severe and early compared to other muscle groups (12; 112). These muscles are enriched in type I (slow-twitch) fibers (96; 16) and are continuously active for postural maintenance, characteristics that may render them vulnerable to cumulative metabolic stress. Subsequently, with aging, paraspinal muscles may display an increased number of cytochrome c oxidase negative fibers, associated with a higher level of mtDNA deletions (12). Given paraspinal muscles have limited functional redundancy and are more difficult to assess during routine bedside strength testing, weakness may be overlooked, which results in major diagnostic delays (02).

Muscle diseases represent one of the most common causes of paraspinal neuromuscular syndromes, whereas motor neuron diseases and neuromuscular junction transmission defects can also present with axial or paraspinal muscle weakness.

Acquired causes

Acquired etiologies account for a substantial proportion of paraspinal neuromuscular syndromes, particularly in middle-aged and older adults, and are more commonly encountered in dropped head syndrome.

Immune-mediated myopathies. Axial or paraspinal-predominant weakness has been reported in idiopathic inflammatory myopathies, including dermatomyositis, immune-mediated necrotizing myopathy, and overlap myositis (02; 98). Indeed, when a diagnosis is established, immune-mediated myopathies are the leading cause of myopathic head syndrome, emphasizing that the condition is potentially treatable (02). In this group, myositis not fitting into any specific diagnostic category is the most common and can be referred to as myositis not otherwise specified (02). Neck extensor weakness, dysphagia, and dysphonia can be presenting symptoms and are noted in all subtypes of idiopathic inflammatory myopathies, but most frequently in overlap myositis associated with scleroderma (95). Axial weakness can also be a rare presentation in granulomatous myositis–like sarcoidosis (11). Graft-versus-host disease myositis, which represents the most common immune-mediated neuromuscular complication of graft-versus-host disease, can present with predominantly axial or proximal muscle weakness (105).

Sporadic late-onset nemaline myopathy (SLONM). Sporadic late-onset nemaline myopathy (SLONM) is a rare myopathy with probable underlying immune mechanisms (75). It can be associated with a monoclonal gammopathy of undetermined significance (MGUS) in approximately 60% of patients, typically of IgG subtype, and can also be associated with HIV (76; 75). SLONM usually manifests with subacute progressive proximal and axial weakness but can also present with chronic progressive weakness mimicking muscular dystrophy (76; 75). In a comprehensive review of SLONM patients, axial weakness was present in 68% of patients, with a mean age at onset of 52 years (107). Muscle MRI show preferential involvement of neck extensors and paraspinal, along with other, proximal muscle groups (74). A systematic review found SLONM-associated MGUS exhibited more severe clinical manifestations, including increased respiratory involvement, more prominent nemaline rods on biopsy, reduced likelihood of full recovery, and higher rates of nonambulatory status (59). Diagnosis is based on identifying nemaline rods on muscle biopsy that preferentially occur in atrophic fibers. Intravenous immunoglobulin is a first-line treatment for all patients; in patients with a monoclonal gammopathy, autologous stem cell transplantation or other plasma cell–directed therapies may be considered, with chemotherapy-based approaches showing superior neurologic improvement rates compared to nonchemotherapy approaches (53).

Inclusion body myositis. Although distal muscles and quadricep weakness are characteristic in inclusion body myositis, the axial muscles may be affected, resulting in camptocormia or head drop (02; 98). Inclusion body myositis can be a common cause of inaugural dropped head or camptocormia, particularly in older patients (01). Severe camptocormia can be the sole clinical manifestation for several years prior to diagnosis, even in the absence of classic quadriceps and finger flexor muscle weakness (66).

Radiation-induced myopathy. Radiation-induced myopathy is a delayed neuromuscular complication resulting from microvascular injury and fibrosis and is most frequently associated with the extended radiation fields used in Hodgkin lymphoma treatment (87). Although it is considered one of the most common neuromuscular complications of radiotherapy, radiation-induced myopathy is characterized by a remarkably long latency period, averaging 15 years, necessitating a careful review of a patient's medical history when they present with axial weakness (37). Clinical presentation often involves axial and periscapular muscle weakness, with head drop occurring more frequently than camptocormia and often accompanied by neck pain (37). As a diagnosis of exclusion, muscle involvement must be strictly confined to the previous radiation field. The presence of myokymic discharges on electromyography can provide strong supportive evidence for the diagnosis when present (37).

Toxic or drug-induced myopathies. Chloroquine and hydroxychloroquine-induced myopathy may commonly present with head drop or neck flexor weakness, often with dysphagia and respiratory involvement (78). Importantly, the myopathy typically improves with cessation of the drug but may be left with some residual weakness. Additional drugs to consider include ranolazine and MEK inhibitors (15; 91). Immune checkpoint inhibitor–associated myositis may also present with head drop (98; 109).

Amyotrophic lateral sclerosis. Although amyotrophic lateral sclerosis typically presents with limb or bulbar weakness, thoracic segment involvement can affect paraspinal muscles. A large retrospective study found that thoracic paraspinal muscle examination on electromyography showed active and chronic denervation more frequently in amyotrophic lateral sclerosis than in non–amyotrophic lateral sclerosis neuromuscular disorders (103). Although axial weakness, including neck extensor and thoracic paraspinal muscles, in amyotrophic lateral sclerosis is typically part of a generalized pattern of motor neuron involvement rather than an isolated or predominant feature, it contributes meaningfully to disability and respiratory compromise (79).

Myasthenia gravis. Dropped head syndrome is uncommon but well-recognized in myasthenia gravis, particularly in muscle-specific kinase (MuSK) antibody-positive or acetylcholine receptor antibody–positive late-onset disease (93; 85). The pathophysiological basis for selective muscle group involvement relates to differences in neuromuscular junction characteristics, safety factors of transmission, and complement protection levels across muscle type (44).

Genetic causes

Genetic etiologies are relevant across the lifespan and can be broadly classified into structural and metabolic muscle diseases. Genetic disorders are more commonly encountered in camptocormia than dropped head syndrome. Additionally, congenital myasthenic syndromes may have prominent head drop at presentation.

Structural genetic muscle diseases. Facioscapulohumeral muscular dystrophy (FSHD) should be considered in any patient presenting with unexplained axial myopathy as it is among the most prevalent inherited myopathies, has a highly variable age of onset, and is not detectable by next-generation sequencing gene panels (02; 122). A cross-sectional study of 87 patients with genetically confirmed FSHD found that eight (9.1%) had camptocormia as the predominant and initial manifestation, and FSHD accounted for 47% of all cases of camptocormia due to axial myopathy in that cohort (122). Compared to classical FSHD, camptocormic patients showed later disease onset, marked axial involvement with predominant spinal extensor weakness and relatively preserved abdominal strength, and moderately contracted D4Z4 repeats (122).

Patients with myotonic dystrophy type 1 or 2 (DM1 or DM2) have been reported with camptocormia with or without head drop (02). In contrast to DM1, which is associated with distal limb, neck flexor, and bulbar weakness, DM2 is associated with predominantly proximal and axial weakness (64). Early detection of myotonic dystrophies is important to manage multisystem symptoms and prevent potential complications, including sudden cardiac death.

Axial muscle weakness specifically affecting the muscles of the neck, spine, and trunk is a defining hallmark of certain LMNA-related myopathies (90; 67). The most distinctive feature is dropped-head syndrome due to profound weakness in the neck extensor muscles. Early-onset cases report failure to achieve or maintain head control, and with disease progression, the axial muscles often undergo fibrosis, leading to a "rigid spine" (90; 46).

Congenital myopathies, including nemaline, core, and centronuclear myopathies, as well as muscular dystrophies affecting nuclear envelope, sarcomeric, or cytoskeletal proteins, show prominent paraspinal involvement and early axial weakness in both childhood- and adult-onset forms. RYR1-related myopathy can have predilection for axial muscles and may present with camptocormia or lumbar hyperlordosis (60; 02). A long-term natural history study of pediatric patients found that scoliosis and spinal rigidity were present in 30% and 17% of patients, respectively. Patients with RYR1 mutations are at increased risk of malignant hyperthermia, and the presence of core or multiminicore formations on muscle biopsy in patients with axial weakness should raise suspicion for RYR1 mutations (60). Mutations in SELENON remain one of the most common causes of rigid spine syndrome, presenting with rigid spine and hyperextension of the neck (130). SELENON-related myopathy is part of a spectrum of multiminicore or core disease and desmin-related myopathy with Mallory body–like inclusions, often accompanied by neuromuscular respiratory insufficiency (114; 130).

Myofibrillar myopathies are a heterogeneous group of rare genetic muscle disorders characterized histopathologically by the disintegration of myofibrils starting at the Z-disk leading to ectopic accumulation of multiple proteins (110). Although these often present with limb-girdle or distal weakness, axial muscle involvement represents a significant yet frequently under-recognized clinical hallmark that can dominate the clinical picture (97), particularly with myotilinopathy (MYOT) and desminopathy (DES), which often present in late adulthood and sometimes remain the isolated first symptom for years before limb weakness develops (108). Rigid spine can be common in presentation for BAG3- and certain FHL1-related myopathies (106; 13).

Genetic metabolic myopathies. Given the high oxidative demands of paraspinal muscles, axial weakness may be an early or dominant feature in metabolic myopathies. Lipid storage myopathy can present with axial myopathy, particularly affecting the neck extensors and paraspinal muscles as documented in several case reports and series, and is primarily caused by late-onset multiple acyl-CoA dehydrogenase deficiency (65; 137). Patients may develop respiratory failure in severe cases. Serum creatine kinase is typically elevated, plasma acylcarnitine profiles show increased levels of various chain intermediates, and riboflavin supplementation can produce significant clinical improvement (120; 133; 101).

Pompe disease (glycogen storage disease type II) is the primary glycogen storage disorder presenting with axial myopathy and is characterized by progressive weakness of paraspinal and limb-girdle muscles due to lysosomal glycogen accumulation from acid alpha-glucosidase deficiency (127). The characteristic pattern includes preferential degeneration of hamstring and paraspinal muscles, correlating with higher glycogen accumulation in these muscle groups (09). Axial weakness has also been reported as a clinical presentation in other glycogen storage disorders like McArdle disease and glycogen storage disease type IV (135; 88).

Mitochondrial myopathy can also present with axial myopathy as a predominant feature and can potentially cause rapidly progressive scoliosis (102; 42).

Head drop in congenital myasthenic syndrome has been most characteristically described with MUSK and COL13A1 mutations, which can cause marked axial weakness, particularly of neck flexion (38; 99). These subtypes present with severe early-onset disease featuring prominent bulbar, respiratory, and facial involvement alongside the characteristic inability to maintain head position against gravity.

Common genetic causes of axial myopathy and rigid spine syndrome are summarized in Table 1 (34; 19; 135; 123; 45; 25; 70).

Table 1. Genetic Causes of Axial Myopathies

Gene	Notes / Phenotype
D4Z4 repeat contraction on chromosome 4q35 with XXX haplotype	Facioscapulohumeral muscular dystrophy. Can present with camptocormia in elderly patients (18; 122)
RYR1	Congenital myopathy, including central core disease and multiminicore disease, with characteristic MRI patterns (47; 82; 84; 134)
SELENON	Rigid spine muscular dystrophy 1 (RSMD1), characterized by poor axial muscle strength, scoliosis, neck weakness, spinal rigidity, and early respiratory insufficiency (47; 19; 123)
LMNA	Emery-Dreifuss muscular dystrophy with cardiac involvement and early spinal contractures (34; 123)
MYH7	Distal and axial phenotype with prominent paraspinal and tongue involvement) (17; 123; 119)
COL6A1–COL6A3 (Collagen VI)	Bethlem myopathy and Ullrich congenital muscular dystrophy with spinal rigidity (123)
DNAJB4	Myopathy with early respiratory failure and spinal rigidity, presenting from infancy to adulthood, with missense variants in the J domain predicting more severe phenotype (45)
HMGCS1	Rigid spine syndrome with scoliosis, neck and spine contractures, hypotonia, and respiratory insufficiency, potentially amenable to mevalonic acid supplementation (25)
GAA	Pompe disease, with late-onset forms presenting with limb-girdle and axial muscle weakness and respiratory dysfunction (52; 127)
DMPK (CCTG repeat expansion) CNBP (CCTG repeat expansion)	DMPK associated with myotonic dystrophy type 1 and CNBP with myotonic dystrophy type 2, both presenting with progressive muscle weakness and myotonia (124; 31)

The genes listed in Table 1 represent the most common and clinically relevant inherited neuromuscular disorders in which dropped head syndrome or predominant axial weakness have been reported. Numerous additional genes have been described in association with axial weakness or dropped head presentation, and comprehensive reviews are available elsewhere (94).

Differential diagnosis

Associated or underlying disorders

Several non–neuromuscular conditions may produce postural abnormalities that resemble paraspinal neuromuscular syndromes. These disorders do not arise from primary weakness of the paraspinal muscles but instead reflect abnormalities of central motor control, movement regulation, spinal structure, or behavior. Distinguishing these entities from true neuromuscular causes is essential, as clinical examination typically reveals preserved paraspinal strength, limited improvement in the supine position, or additional neurologic, structural, or psychiatric features that point to an alternative mechanism. The following conditions, listed in Table 2, should, therefore, be considered important mimics in the differential diagnosis of paraspinal neuromuscular syndromes.

Table 2. Mimics of Paraspinal Neuromuscular Syndromes

Category	Condition	Distinguishing features
Movement disorders	Parkinson disease	Flexed posture without true paraspinal weakness; rigidity and bradykinesia; poor correction in supine position
	Atypical parkinsonism (eg, multiple system atrophy, progressive supranuclear palsy)	Early postural instability; autonomic or ocular motor features; limited response to levodopa
	Truncal dystonia	Sustained or task-specific abnormal postures; may fluctuate; normal strength on testing
Neurodegenerative dementia	Alzheimer disease, frontotemporal dementia	Postural changes related to apraxia or executive dysfunction rather than weakness
Spinal and structural disorders	Ankylosing spondylitis	Fixed kyphosis; limited spinal mobility
	Vertebral compression fractures	Acute or subacute pain; focal tenderness; radiographic deformity
	Degenerative spine disease	Mechanical pain; radicular symptoms; imaging correlates
Drug-related postural syndromes	Antipsychotic-induced dystonia	Exposure history; sustained muscle contractions; reversibility with medication changes
Psychiatric / functional disorders	Functional postural disorder	Inconsistent examination; distractibility

Diagnostic workup

	• Detailing the clinical phenotype and histopathological findings are key elements to establish a diagnosis.
	• If due to neuromuscular axial weakness, the abnormal posture should resolve in the supine position, helping distinguish it from mechanical or CNS disorders.
	• EMG and MRI can guide muscle biopsy and genetic testing.

The diagnostic approach to paraspinal neuromuscular syndromes requires systematic exclusion of non-neuromuscular causes before pursuing extensive neuromuscular investigations. The critical initial step is distinguishing true neuromuscular weakness from mechanical spinal deformity and movement disorders (33; 26). A key clinical feature is that bent spine syndrome or dropped head syndrome due to muscle weakness typically resolve completely in the supine position, whereas mechanical spinal deformities persist even when lying flat (33; 61). This postural correction strongly suggests a neuromuscular etiology rather than structural spinal pathology.

Exclusion of dystonia and parkinsonism is essential before attributing axial weakness to neuromuscular disease (61; 26; 07). Camptocormia in Parkinson disease usually results from axial dystonia rather than true muscle weakness. As dystonia is due to forceful contraction of muscles, the abnormal posture initially persists in the supine position; however, it may slowly subside with relaxation or alleviating maneuvers. Accompanying signs, such as tremor, bradykinesia, rigidity, and characteristic gait abnormalities, are helpful clues when present (61; 07).

Lastly, detecting weakness on muscle strength testing in other limb or cranial muscles would suggest a neuromuscular etiology rather than a movement disorder.

Laboratory testing. Serum creatine kinase (CK) can be helpful in indicating underlying myopathy, but levels may vary depending on etiology (20; 95). Necrotizing autoimmune myopathies typically demonstrate markedly elevated CK (up to 50 times the upper limit of normal), whereas inflammatory myopathies show moderate elevation (5–10 times normal) (20). CK may be normal or only mildly elevated in dermatomyositis, overlap myositis, and inclusion body myositis despite active disease. CK can be normal in late-onset Pompe disease despite significant muscle involvement, emphasizing that normal CK does not exclude metabolic myopathy (131; 69). Aspartate aminotransferase and alanine aminotransferase are often elevated and may be erroneously attributed to liver disease (20).

Myositis-specific and myositis-associated autoantibodies are present in approximately two thirds of patients with idiopathic inflammatory myopathies and should be routinely checked in the appropriate clinical setting (98; 95). Screening for a connective tissue disorder, especially scleroderma, could be considered. For suspected myasthenia gravis presenting with isolated neck extensor weakness, acetylcholine receptor (AChR) antibodies should be tested (71; 93; 41). MuSK antibodies should be considered in AChR antibody-negative patients, particularly those with prominent bulbar and neck weakness.

For suspected metabolic myopathies, screening for enzyme deficiency or abnormal metabolite levels, such as acylcarnitine profile, can aid in the diagnosis. A simple blood-based assay to measure alpha-glucosidase activity is the optimal screening test for treatable Pompe disease (52; 131) and should be routinely considered for late-onset axial weakness or neuromuscular respiratory symptoms. Serum lactate levels in adults with mitochondrial myopathies have low sensitivity (08). GDF15 levels have higher sensitivity (80). However, its specificity in clinical practice is suboptimal as it can be elevated in various conditions (32). Endocrine disorders of the thyroid and parathyroid should also be ruled out in axial weakness (132).

Electrodiagnostic evaluation. Electromyography is crucial to confirming a neuromuscular etiology and determining the localization: muscle versus neuromuscular junction versus motor neurons (135; 02; 28). Repetitive nerve stimulation showing decremental response supports neuromuscular junction disorders, whereas single-fiber EMG has 97% sensitivity but only 70% specificity for myasthenia gravis (41).

Clinical examination is important prior to EMG to ensure sampling for weak muscles. Paraspinal muscle sampling is critical and, in this context, has higher diagnostic yield than limb muscles in patients with axial myopathy (135; 02). EMG in myopathy typically demonstrates short-duration, low-amplitude polyphasic motor unit potentials with early recruitment (20; 95). Fibrillation potentials and positive sharp waves are common and can be due to inflammation, necrosis, vacuolization, or secondary denervation (77; 111; 43).

However, EMG findings can sometimes be misleading in axial myopathies as neuropathic changes are not uncommon, especially in cervical and lumbar regions (28). Thoracic paraspinals or other surrounding cervical muscles, such as splenius capitis or trapezius, would also be of high yield in the appropriate clinical context.

The presence of myotonic discharges on EMG should prompt further evaluation, including possible genetic testing for myotonic dystrophy (63; 124). However, electrical myotonia on EMG without clinical myotonia can be encountered in various acquired and inherited myopathies, especially those with a marked necrotizing component (77).

Muscle imaging. Muscle MRI is invaluable for detecting paraspinal muscle involvement, guiding biopsy site selection, and distinguishing myopathies from mimics (86; 135; 95; 117). T2-weighted or STIR sequences detect muscle edema reflecting active inflammation, whereas T1-weighted sequences identify fatty replacement and atrophy (135; 21). Quantitative MRI with fat fraction measurement and water T2 mapping can be used to monitor disease activity and treatment response when available (95).

Specific MRI patterns can suggest particular diagnoses (81). In a facioscapulohumeral muscular dystrophy cohort, paraspinal fat fraction averaged 38% compared to 20% in controls, with severity correlating with D4Z4 repeat size (18), suggesting camptocormia may be a phenotypic variant in elderly patients (122). MYH7-related myopathy with axial involvement shows prominent atrophy and fatty infiltration of paraspinal muscles and tongue, with occasional distinctive patterns in limb muscles (17). In metabolic myopathies, paraspinal muscle involvement is common: McArdle disease shows fat replacement of paravertebral muscles in all affected patients on MRI, with frequent involvement of the tongue and subscapularis (04; 121). Pompe disease demonstrates limb-girdle and paraspinal muscle involvement on MRI (127).

In hereditary myopathies presenting with rigid spine syndrome, whole-body MRI can differentiate specific genetic causes with high accuracy (94.3%) (123). RYR1-myopathy demonstrates specific MRI patterns that can guide diagnosis (47; 84). Even when limb involvement is not clinically apparent, screening for MRI patterns to help with diagnosis can be considered, especially in inconclusive cases.

Genetic testing. When hereditary myopathy is suspected based on family history, early onset, or specific clinical or imaging patterns, targeted next-generation sequencing gene panels or whole-exome sequencing should be pursued (82; 119; 134; 14). Multi-gene panels for muscular dystrophies and myopathies have diagnostic yields of 46% to 61% when used as first-tier testing (47; 134; 14). Genetic testing is particularly valuable when muscle biopsy is nondiagnostic or shows nonspecific changes, when the phenotype suggests a specific genetic syndrome, or when protein analysis on muscle biopsy indicates a particular protein deficiency (82; 17; 119). For repeat expansion disorders, such as myotonic dystrophy and facioscapulohumeral muscular dystrophy, specific genetic testing is required as standard NGS panels do not reliably detect repeat expansions (119). Whole genome sequencing could also cover repeat expansion disorders, depending on the laboratory.

Muscle biopsy. Muscle biopsy remains essential for the definitive diagnosis of most paraspinal myopathies, especially in the absence of a family history with similar phenotype, lack of features suggestive of an inherited disorder, or when genetic testing is inconclusive (20). The splenius capitis muscle has the highest diagnostic yield (67%) for muscle biopsy in dropped head syndrome, though paraspinal muscles can also be sampled (02). MRI or ultrasound guidance improves biopsy yield by targeting muscles with active inflammation while avoiding end-stage muscles with complete fatty replacement (20; 95). Given the limited access to sampling of axial muscles in some institutions and the associated challenges in interpretation, limb muscles may be targeted instead, provided they are clinically involved or show abnormalities on EMG or on imaging.

Histopathological findings vary by disease subtype. Dermatomyositis histopathological findings include perivascular inflammation and perifascicular atrophy or predilection of myofiber abnormalities to the perifascicular regions, along with capillary depletion and complement deposit on capillaries (20; 55). Increased myxovirus A expression in the perifascicular region is the most commonly encountered finding in dermatomyositis with very high specificity (126; 125). Immune-mediated necrotizing myopathy demonstrates scattered necrotic and regenerating muscle fibers with relatively minimal inflammation (95). Inclusion body myositis is characterized by endomysial inflammation invading non-necrotic fibers, rimmed vacuoles, protein aggregates, and mitochondrial abnormalities (62).

Nemaline myopathy is characterized by the presence of nemaline rods (nemaline bodies) in muscle fibers, best visualized with modified Gömöri trichrome staining showing characteristic, purple-colored rods. Nemaline rods are detected in patients with SLONM and are usually encountered in atrophic muscle fibers (75) with minimal or no inflammation (76; 118).

Core myopathies (central core disease and multiminicore disease) are characterized by focally reduced oxidative enzyme activity ("cores") in muscle fibers and are most commonly seen in RYR1- and SELENON-related myopathies (47; 84).

Pompe disease (acid maltase deficiency) shows periodic acid-Schiff (PAS)-positive vacuolar myopathy with glycogen accumulation in lysosomes (52; 131). Muscle biopsy in Pompe disease may show minimal changes early in the disease course, with more severe dystrophic changes developing over time (05).

Muscle biopsies in chloroquine or hydroxychloroquine-induced myopathy typically reveal a vacuolar myopathy characterized by rimmed vacuoles, marked acid phosphatase reactivity, and myeloid or curvilinear bodies on electron microscopy (78). In contrast, ranolazine-induced myopathy presents as a lipid storage myopathy with excessive lipid accumulation and vacuolation predominantly affecting type 1 myofibers (91).

A muscle that has recently undergone EMG should not be avoided as needle trauma can cause artifactual changes. In 10% to 20% of cases, muscle biopsy findings are inconclusive due to sampling error from scattered distribution of pathological abnormalities (95).

Management

Outcomes

	• Treatment is entirely dependent on establishing the underlying etiology, as acquired causes often have effective therapies, whereas genetic myopathies without enzymatic replacement are managed supportively.
	• Respiratory involvement is common and potentially life-threatening. Routine pulmonary function testing and overnight oximetry should be performed at diagnosis and during following. A sleep study and referral to Sleep medicine is warranted for patients with symptomatic neuromuscular respiratory insufficiency.
	• Comprehensive multidisciplinary care, including physical and occupational therapy, respiratory therapy, swallow evaluation, cardiac surveillance for relevant genetic conditions, and orthotic devices, improves quality of life and outcomes.

The management of paraspinal neuromuscular syndromes is entirely dependent on establishing the underlying etiology, either acquired or inherited, each requiring fundamentally different therapeutic strategies (02). Thus, accurate diagnosis is the critical first step in determining appropriate management, as treatment efficacy is closely linked to the specific underlying pathology.

When paraspinal neuromuscular syndromes manifest as a presentation of myasthenia gravis, axial weakness often improves with treatment (113). The treatment approach for myasthenia gravis with axial involvement follows the same principles as generalized myasthenia gravis. Corticosteroid treatment is generally accepted as first-line immunosuppressive treatments, aiming for remission by using high daily doses and then reducing to a low maintenance dose with or without the addition of non-steroid immunosuppression (129). The landscape of myasthenia gravis treatment, however, is an evolving field and currently includes several other agents, such as intravenous immunoglobulins, plasma exchange, FcRn antagonists, and complement inhibitors (129; 10).

The treatment strategy for inflammatory myopathies varies depending on each entity. High-dose glucocorticoids remain the mainstay of treatment with tapering guided by clinical improvement (95). Steroid-sparing agents, such as azathioprine, methotrexate, tacrolimus, or mycophenolate mofetil, are commonly used. There is increasing use of intravenous immunoglobulin, particularly given it is not an immunosuppressive therapy. It remains the only FDA-approved treatment for myositis, namely for dermatomyositis. Rituximab or other aggressive therapies should be considered in patients with refractory disease (95). Of note, immune-mediated myopathies with no inflammation on biopsy, such as immune-mediated necrotizing myopathy or SLONM, do not respond well to oral prednisone or immunosuppressants (48; 76). IVIG should be used as first line in these disorders. In SLONM, patients who do not respond to intravenous immunoglobulin (IVIg) therapy and who have an associated monoclonal gammopathy are typically considered for more aggressive treatment approaches, particularly chemotherapy-based regimens or autologous stem cell transplantation (76).

For metabolic myopathies presenting with predominant axial involvement, treatment strategies vary based on the specific enzymatic defect. In late-onset Pompe disease, enzyme replacement therapy is the standard of care (36). For other glycogen storage disorders, treatment strategies follow disease-specific mechanisms. There is no cure or obvious treatment for mitochondrial myopathies, with current treatment largely supportive and possibly including vitamins and cofactor supplements (06). For lipid storage myopathy from the multiple acyl-CoA dehydrogenase deficiency (MADD) phenotype, riboflavin supplementation can be highly effective, with or without carnitine supplementation (133).

For genetic myopathies without specific enzymatic replacement or metabolic therapies, treatment is mainly supportive, focusing on maintaining function and quality of life through comprehensive multidisciplinary management. This includes monitoring and management of respiratory complications, nutritional support, and orthopedic interventions, as needed.

Physical therapy and exercise remain an important component of comprehensive management, particularly for conditions without cure or treatment, with various exercise subtypes of aerobic/endurance or strength/resistance training being generally beneficial and potentially improving muscle endurance and functional outcome (68). Exercise therapies are generally safe and well-tolerated although lacking optimal protocols (68).

Dysphagia can be frequently associated with dropped head syndrome (02) and, hence, should be routinely evaluated and managed when indicated.

Genetic diagnosis is central to predicting cardiac involvement patterns. Initial cardiac evaluation should include physical examination, ECG, and echocardiography at the time of genetic diagnosis, with subsequent surveillance frequency and modalities determined by the specific gene mutation and its associated cardiac phenotype—arrhythmic risk versus cardiomyopathy risk (31).

Early management of respiratory symptoms is crucial. Spirometry with forced vital capacity or slow vital capacity, maximum inspiratory and expiratory pressures (MIP/MEP) or sniff nasal inspiratory pressure (SNIP), and peak cough flow (PCF) should be performed at diagnosis and at least every 6 months in patients at risk of respiratory failure (50). Supine and upright forced vital capacity (FVC) measurements can detect diaphragmatic weakness, with a supine fall over 25% suggesting significant diaphragmatic involvement (50). Thresholds for concern include FVC under 80% of predicted, maximum inspiratory pressure (MIP) under 40 cm H₂O, and peak cough flow (PCF) under 270 L/min in individuals 12 years of age or older. Personalized respiratory physiotherapy can enhance patients' ability to participate in muscle training exercises (23).

Comprehensive multidisciplinary care involving physical therapy, occupational therapy, speech-language pathology, and respiratory therapy has been associated with improved quality of life, resource utilization, and health outcomes and, hence, are routinely recommended in the care of neuromuscular patients (89).

Conservative management with orthotic devices represents an additional supportive approach for axial weakness in neuromuscular disease. Cervical collar application combined with active neck range of motion exercises can be successful in selected patients when applied for a few months (72). For camptocormia, spinal orthotic devices like collars, abdominal binders, and spinal braces may improve quality of life, pain symptoms, and balance, but compliance can be limited due to discomfort (22; 51).

Surgical intervention should be reserved for carefully selected patients, as surgery in neuromuscular disease is associated with substantial complications (29). Wound-related complications and respiratory complications remain the most common complications after corrective surgery, with implant failure and a high pooled rate of revision surgery being other reported challenges (92).

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Contributors

All contributors' financial relationships have been reviewed and mitigated to ensure that this and every other article is free from commercial bias.

Authors

Pritikanta Paul MD

Dr. Paul of UCSF School of Medicine has no relevant financial relationships to disclose.
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Elie Naddaf MD

Dr. Naddaf of Mayo Clinic, Rochester, received consulting fees from Expert Connect, Arcellx, and Jansen; he received a presentation fee from WebMD.
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Editor

Nicholas E Johnson MD MSCI FAAN

Dr. Johnson of Virginia Commonwealth University received consulting fees and/or research grants from AMO Pharma, Avidity, Dyne, Novartis, Pepgen, Sanofi Genzyme, Sarepta Therapeutics, Takeda, and Vertex, consulting fees and stock options from Juvena, and honorariums from Biogen Idec and Fulcrum Therapeutics as a drug safety monitoring board member.
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Former Authors

Jonathan Katz MD
Richard J Barohn MD
Thomas Klopstock MD
Loulwah Mukharesh MD
Khaled Albazli MD
Abdulaziz Almaghraby MD
Prarthana Hareesh MD MPH
Elham Bayat MD
Emma Ciafaloni MD FAAN

Patient Profile

Age range of presentation: 0 months to 65+ years
Sex preponderance: Primary camptocormia

female>male, 3:1

Isolated neck extensor myopathy

male=female
Heredity: Isolated neck extensor myopathy

none

Primary camptocormia

heredity may be factor

autosomal dominant
Population groups selectively affected: None selectively affected
Occupation groups selectively affected: None selectively affected

ICD & OMIM codes

ICD-10: Dorsopathy, unspecified: M53.9

Camptocormia: F44.8
ICD-11: Symptom or complaint of the neck: ME86.C

Localised spinal muscular atrophy: 8B61.4

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Paraspinal neuromuscular syndromes

Associated Disorders

Dropped head syndrome

Differential Diagnosis

Parkinson disease
atypical parkinsonism
multiple system atrophy
progressive supranuclear palsy
truncal dystonia
- Alzheimer disease
- frontotemporal dementia
- ankylosing spondylitis
- vertebral compression fractures
- degenerative spine disease
- antipsychotic-induced dystonia
- functional postural disorder

Paraspinal neuromuscular syndromes …

Paraspinal neuromuscular syndromes

Cite this article

Introduction

Overview

Key points

Historical note and terminology

Clinical manifestations

Presentation and course

Prognosis and complications

Biological basis

Etiology and pathogenesis

Acquired causes

Genetic causes

Table 1. Genetic Causes of Axial Myopathies

Differential diagnosis

Associated or underlying disorders

Table 2. Mimics of Paraspinal Neuromuscular Syndromes

Diagnostic workup

Management

Outcomes

References

Contributors

Authors

Editor

Former Authors

Patient Profile

ICD & OMIM codes

This is an article preview.
Start a Free Account
to access the full version.

Questions or Comment?

Also in This Category

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Drug-induced myasthenic syndromes

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Givinostat

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Rozanolixizumab-noli

Efgartigimod alfa-fcab

Paraspinal neuromuscular syndromes

Cite this article

Introduction

Overview

Key points

Historical note and terminology

Clinical manifestations

Presentation and course

Prognosis and complications

Biological basis

Etiology and pathogenesis

Acquired causes

Genetic causes

Table 1. Genetic Causes of Axial Myopathies

Differential diagnosis

Associated or underlying disorders

Table 2. Mimics of Paraspinal Neuromuscular Syndromes

Diagnostic workup

Management

Outcomes

References

Contributors

Authors

Editor

Former Authors

Patient Profile

ICD & OMIM codes

This is an article preview. Start a Free Account to access the full version.

Questions or Comment?

Also in This Category

Viral and retroviral myositis

Drug-induced myasthenic syndromes

Reducing body myopathy

Givinostat

Zilucoplan

Efgartigimod alfa and hyaluronidase-qvfc

Rozanolixizumab-noli

Efgartigimod alfa-fcab

This is an article preview.
Start a Free Account
to access the full version.