Resident Physician Mount Sinai Hospital New York, New York, United States
Case Diagnosis: Hirayama Disease
Case Description: Mr. A is a 39 year old man with prior anterior discectomy and fusion of C4-7 in 2005, revision in 2017, posterior laminectomy and fusion from C2-T2 in 2018. Patient was scheduled for revision of fusion for progressive bilateral hand paresthesias and weakness but presented early due to acutely worsening neck pain after a fall. Imaging demonstrated displaced and broken screws. Post revision and extension of fusion, patient was admitted to inpatient rehabilitation with significant right greater than left distal upper extremity weakness, specifically finger abduction and flexion, atrophy of hypothenar, thenar, and intrinsic hand muscles. Neurological testing of lower extremities were unremarkable. Sensation was grossly intact. Patient’s upper extremity weakness began at age 8 and progressively worsened. Patient was without other neurologic or genetic conditions.
Discussions: Hirayama disease is a rare, often self-limiting, cervical myelopathy, predominant in males. Patients present as adolescents with slow asymmetric progressive muscle weakness and atrophy of distal upper musculature. During neck flexion, forward displacement of the posterior sac leads to spinal cord compression. Typically, there is no involvement of the lower extremity, eventual stabilization, no sensory or reflex abnormalities. This disease is best evaluated by a cervical flexion MRI, with findings of asymmetric medullary flattening, prominence of the posterior epidural venous plexus, and anterior movement of the posterior dural sac during neck flexion. For this patient, after review of history and prior imaging, neurosurgery suspected Hirayama disease. No other diagnosis explained the early onset weakness and worsening myelopathic changes in areas well decompressed. Unfortunately, diagnosis could not be confirmed due to inability of patient to remain flexed during MRI.
Conclusions: Literature describing Hirayama disease is limited. Patients should be recognized early and placed in a cervical collar. Rehabilitation focuses on strengthening of the distal musculature, coordination, and avoidance of flexion based exercises until resolution.