[Monomelic amyotrophy. Report of one case].

Area of Science:

• Neurology
• Neuroscience
• Clinical Medicine

Background:

• Monomelic amyotrophy, or Hirayama disease, is a rare lower motor neuron syndrome characterized by cervical spinal cord pathology.
• It typically manifests in young adults with insidious onset of unilateral hand and forearm weakness and atrophy.

Observation:

• A 19-year-old male presented with a two-year history of progressive unilateral weakness and atrophy in his right hand.
• Neurological examination revealed intrinsic hand muscle atrophy and weakness, with sparing of specific muscles.
• Forearm atrophy was noted, sparing the brachioradialis muscle.

Findings:

• Electromyography indicated active and chronic neurogenic changes in C8 and T1 myotomes, with mild changes in C7.
• Cervical spine MRI showed spinal cord atrophy from C5 to C7 segments.
• Imaging revealed forward displacement of the posterior dura in cervical flexion, a characteristic finding.

Implications:

• The combination of clinical presentation, electrophysiological data, and MRI findings strongly supports the diagnosis of monomelic amyotrophy.
• Early and accurate diagnosis is crucial for managing this progressive condition.
• Understanding the imaging correlates, particularly dural ectasia in flexion, aids in differentiating Hirayama disease from other neuropathies.