Myoclonus epilepsy with ragged-red fibers
Jun. 10, 2021
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Neuromuscular syndromes of the paraspinal muscles comprise the dropped head syndrome and the bent spine syndrome (camptocormia). Although these phenotypes also occur in conjunction with dystonia or Parkinson disease, large series suggest that the majority of cases are due to an isolated paraspinal myopathy or are a prominent part of a more widespread myopathy, neuromuscular junction disorder, neuropathy, or motor neuron disease. Even camptocormia and dropped head syndrome in Parkinson disease are often due to myopathic changes in the paraspinal muscles. In this article, the authors discuss advantages and disadvantages of paraspinal muscle biopsies for diagnostic purposes. In any event, histology has to be interpreted with caution because these particular muscles show a variety of neuromuscular abnormalities even in healthy subjects.
• Weakness of the paraspinal muscles may lead to dropped head syndrome or bent spine syndrome (camptocormia).
• The phenotypes of the dropped head and bent spine syndromes may be caused by many underlying etiologies, but the majority of cases seem to be due to an isolated paraspinal myopathy or provide a prominent sign of a more widespread myopathy.
• Clarifying the etiology in every single case has an impact on therapy because dystonic forms may respond to sensory tricks or botulinum toxin therapy, and parkinsonian forms may respond well to deep brain stimulation.
In 1986, Lange and colleagues described severe neck extensor weakness, using the term “floppy head syndrome” (51). The floppy head syndrome occurred as part of a generalized neuromuscular disorder, such as myasthenia gravis, polymyositis, or motor neuron disease, in 9 of 12 patients; in the other 3 there was no apparent cause for the neck weakness. In 1992, Suarez and Kelly elaborated on the same clinical manifestations, now favoring the words “dropped head syndrome” (96). They described 4 patients with a noninflammatory myopathy primarily affecting the lower cervical and upper thoracic paraspinal muscles. The patients had mild limb girdle weakness in addition to severe neck weakness. A subsequent report suggested that an important cause of the head drop is an isolated myopathy of the neck extensor muscles (43). These patients did not have extremity weakness, and using the term “isolated neck extensor myopathy,” a specific disorder was distinguished from other neuromuscular conditions that also cause neck weakness. In contrast, the terms “dropped head syndrome” or “dropped head sign” are best used to describe the phenomenology regardless of the underlying cause.
A related disorder of paraspinal muscles has been referred to as the “bent spine syndrome” or “camptocormia.” The latter is derived from the Greek: kamptos for bent and kormos for trunk. It is defined as an involuntary reversible flexion of the cervical or thoracolumbar spine, which worsens while walking and standing and improves in the supine position, and therefore differentiates it from kyphosis. There was a painting prior to World War I illustrating a camptocormic subject as early as the 1600s by the Spanish painter Francisco de Zurbarán (1598-1664) in San Hugo en el refectorio de los Cartujos (28; Tatu and Bogousslavsky 2017). The term “camptocormia” was first recognized and officially described by the French neurologist Souques during World War I in soldiers who acutely developed an anteriorly flexed trunk (39). That condition was thought to be psychogenic and lasted only a few months. In the last decades, however, camptocormia has been described in association with Parkinson disease (17), multiple system atrophy (03), dystonias (77), and other neuromuscular disorders marked by weakness of the thoracic, lumbar, or sacral paraspinal muscles (91; 102). As with the dropped head syndrome, the differential diagnosis in patients with a bent spine includes other generalized neuromuscular disorders and an isolated focal paraspinal myopathy or “axial myopathy.”
In a large retrospective series of 63 patients with bent spine syndrome, 40 had isolated paraspinal myopathy with fatty infiltration and lobular endomysial fibrosis; 19 had more widespread signs of myopathy (including 8 cases of limb girdle muscular dystrophy, 3 myotonic dystrophy type I, 2 facioscapulohumeral dystrophy, and 2 inclusion body myositis); and 4 had Parkinson disease without paraspinal myopathy (52). On the other hand, there is some evidence that camptocormia and head drop syndrome in Parkinson disease are predominantly myopathic. In a series of 17 Parkinson patients with camptocormia or head drop, histopathology revealed chronic myopathic changes in 14 of 17 biopsies consisting of abnormal variation in fiber size; increase in internal nuclei; and increase in connective tissue, myofibrillar disarray, and similarities to protein surplus myopathies (95). The authors speculate that aberrant protein aggregation may link Parkinson disease and camptocormia. A study by Whittaker and colleagues reported an unusual case of a 49-year-old male patient who presented with camptocormia as the initial symptom of his Parkinson disease, in contrast to the usual late presenting camptocormia in advanced stages of Parkinson disease. A muscle biopsy was obtained that showed CD8 lymphocytic infiltration, and his camptocormia did not respond to L-dopa, but it significantly improved with prednisolone, all of which led to the theory of a possible idiopathic autoimmune etiology in association with his Parkinson disease (109). It is not clear whether the classic “stooped” appearance of parkinsonian patients represents mild forms of antecollis/camptocormia. This uncertainty reflects the lack of a clear clinical definition and the different thresholds that physicians use for diagnosis. Most authors propose that a marked (minimum 45°) flexion in the sagittal plane should be required to diagnose antecollis and camptocormia, respectively. It seems likely, however, that the postural deformities in Parkinson disease have a multifactorial pathophysiology. Contributing factors include muscular rigidity, axial dystonia, weakness caused by myopathy, body scheme defects, and structural changes in the spine. Clarification of the relative contribution of these different factors may help to define clear diagnostic criteria and ultimately lead to improved treatment approaches (18).
An entity that is similar to camptocormia but is thought to be related to Parkinson disease or induced by medications as a side effect is called “Pisa syndrome,” where involuntary reversible lateral bending (minimum 10°) of the trunk occurs while walking or standing and improves in the supine position or by passive mobilization (05; 101). Medication-induced Pisa syndrome includes levodopa drugs (94; 11), ropinirole (27), donepezil, and rivastigmine (49).
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