Cerebral hypotonia

Mihee J Bay MD (Dr. Bay of Kennedy Krieger Institute and Johns Hopkins School of Medicine has no relevant financial relationships to disclose.)
Michael V Johnston MD, editor. (Dr. Johnston of Johns Hopkins University School of Medicine and Chief Medical Officer at Kennedy Krieger Institute has no relevant financial relationships to disclose.)
Originally released July 12, 2006; last updated February 1, 2016; expires February 1, 2019

This article includes discussion of cerebral hypotonia, central hypotonia, essential hypotonia, benign congenital hypotonia, and floppy infant. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Hypotonia is a clinical manifestation of numerous diseases affecting the central and/or peripheral motor nervous system. The key to accurate diagnosis involves integral steps of evaluation that include a detailed history, examination, and diagnostic tests. “Cerebral” (or central) hypotonia implies pathogenesis from abnormalities from the central nervous system, and related causal disorders include cerebral dysgenesis and genetic or metabolic disorders. Patients with central hypotonia generally have hypotonia without associated weakness, in contrast to the peripheral (lower motor neuron) causes, which typically produce both hypotonia and muscle weakness. Hypotonia is a clinical manifestation of over 500 genetic disorders; thus, a logical, stepwise approach to diagnosis is essential. With recent advances in the field of genetic testing, diagnostic yield will undoubtedly improve. There is no cure, but treatment includes supportive therapies, such as physical and occupational therapy, and diagnosis-specific management.

Key points

 

• Hypotonia is reduced tension or resistance of passive range of motion.

 

• The first step in the evaluation of a child with hypotonia is localization to the central (“cerebral”) or peripheral nervous system, or both.

 

• Central hypotonia is more likely to be noted axially with normal strength and hyperactive to normal deep tendon reflexes.

 

• Other clues to central hypotonia include dysmorphic facies, macro or microcephaly, developmental delay (global, motor, or cognitive), seizures, malformations of other organs, altered level of consciousness, abnormal eye movements, abnormal breathing pattern, or other signs of central nervous system dysfunction.

 

• A majority of diagnoses arise from history and physical exam, but neuroimaging, genetic testing, and other laboratory evaluations are also important in diagnosis.

Historical note and terminology

The term “cerebral hypotonia” describes a symptom complex concerning the contribution of higher cortical functions to muscle tone and motor development.

Literature in the 1960s reflects an understanding of the cerebral influences on tone and motor control. In 1961, Jebsen and colleagues suggested classification of the causes of hypotonia into 3 broad categories: (1) central nervous system diseases, (2) motor unit diseases, and (3) metabolic disorders (Jebsen et al 1961). Furthermore, the monograph by Victor Dubowitz in the late 1960s entitled “The Floppy Infant” provided a practical approach to the diagnosis and classification of a child with hypotonia (Dubowitz 1969). He emphasized 2 main questions when confronted with a floppy baby or child: (1) “Is this a paralyzed child with incidental hypotonia?” and (2) “Is this a hypotonic child without significant muscle weakness?” His categorization of the paralytic conditions of children with hypotonia with weakness with “incidental” hypotonic was found to be most often lower motor neuron diseases: proximal spinal muscular atrophies, congenital myopathies, and other neuromuscular disorders. The infants with nonparalytic conditions who had hypotonia without significant weakness included disorders of the central nervous system, connective tissue disorders, metabolic, nutritional, and endocrine disorders, acute illness, and essential (or benign) hypotonia. This subdivision, central versus peripheral hypotonia, remains clinically useful. Two thorough reviews of the genetic evaluation of hypotonia provide diagnostic algorithms based on the original distinction of symptom manifestations: central, peripheral, or both (Lisi and Cohn 2011; Prasad and Prasad 2011). A concise overview of neonatal hypotonia is also presented in a recent review article (Sparks 2015).

At the end of his monologue Dubowitz stated, “It is important for the clinician to remember that when he makes the diagnosis of floppy infant syndrome, he is only at the beginning of the diagnostic exercise not at the end.”

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