page_title: Congenital distal spinal muscular atrophy
section_title: Diagnosis
hierarchical_section_title: Congenital distal spinal muscular atrophy / Diagnosis
caption_attribution_description: English: Intermediate magnification micrograph of denervation atrophy of type 2 fibres. HPS stain. Muscle biopsy. There is fibre type group, group atrophy and prominent target fibres. The ATP9.4 stain demonstrates atrophy of type 2 fibres. Related images Intermed. mag. High mag. Very high mag. High mag. SDH. Very high mag. SDH. Intermed. mag. ATPase pH 9.4. High mag. ATPase pH 9.4.
context_page_description: Congenital distal spinal muscular atrophy is a hereditary condition characterized by muscle wasting, particularly of distal muscles in legs and hands, and by early-onset contractures of the hip, knee, and ankle. Affected individuals often have shorter lower limbs relative to the trunk and upper limbs. The condition is a result of a loss of anterior horn cells localized to lumbar and cervical regions of the spinal cord early in infancy, which in turn is caused by a mutation of the TRPV4 gene. The disorder is inherited in an autosomal dominant manner. Arm muscle and function, as well as cardiac and respiratory functions are typically well preserved.
context_section_description: Electrophysiological evidence of denervation with intact motor and sensory nerve conduction findings must be made by using nerve conduction studies, usually in conjunction with EMG. The presence of polyphasic potentials and fibrillation at rest are characteristic of congenital dSMA.
  The following are useful in diagnosis:
  Nerve conduction studies (NCS), to test for denervation
  Electromyography (EMG), also to detect denervation
  X-ray, to look for bone abnormalities
  Magnetic resonance imaging (MRI)
  Skeletal muscle biopsy examination
  Serum creatine kinase (CK) level in blood, usually elevated in affected individuals
  Pulmonary function test
caption: Denervation atrophy
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