Proximal and proximo-distal bimelic amyotrophy: Evidence of cervical flexion induced myelopathy

Abstract

This report aims at describing two new clinical phenotypes associated with classical features of cervical flexion induced myelopathy (CFIM). The description is of a prospective case series of six young males presenting with progressive bilateral proximal/proximo-distal amyotrophy of upper limbs and demonstrating the typical MRI characteristics of Hirayama disease. All underwent detailed clinical, electrophysiologcal and imaging studies. The affected muscles were shoulder girdles and arms in proximal form (n = 2) and the entire upper limbs in proximo-distal form (n = 4). The mean age at onset was 21.0 ± 3.3 years, duration of illness was 6.7 ± 3.4 years, period of progression was 39.0 ± 27.3 months followed by a stable phase of 45.0 ± 50.0 months. All had severe wasting and weakness of affected muscles leading to significant disability. Nerve conduction studies revealed grossly reduced compound muscle action potential amplitudes with neurogenic pattern on electromyography of affected muscles. On MRI all revealed evidence of cervical cord atrophy with signal changes, dural detachment and extensive posterior epidural enhancement (variably from C1 to T2 level). Altered cervical curvature was prominent. In conclusion, hitherto unreported, we describe two additional clinical phenotypes (proximal and proximo-distal forms) of Hirayama disease demonstrating the cardinal imaging features of CFIM.

Update on the Pathogenesis, Clinical Diagnosis, and Treatment of Hirayama Disease

“…Preethish-Kumar et al showed that distal, proximal, and proximodistal bimelic amyotrophy are all myelopathies that can be induced by cervical flexion (40). Thus, the functional outcome of proximal forms is likely worse and more uncertain than that of distal forms (14,56).…”

Hirayama disease: Nosological classification and neuroimaging clues for diagnosis

“…coined the term “Distal BiMelic Amyotrophy” (DBMA) to describe a symmetrical amyotrophy of the distal upper extremities with rapid progression to severe motor disability and showing similar MRI features with the previously described entity of MMA/HD (eg, flexion‐induced cervical myelopathy at C8‐T1 myelomers) 9 . Also, the flexion‐induced myelopathy may spread from C8‐T1 myelomeres to two segment higher or lower than MMA/HD (eg, C5‐T1 myotomes), leading to a “Proximal BiMelic Amyotrophy” (PBMA) or “Proximo‐Distal biMelic Amyotrophy” (PDMA) 10 . However, the absence of sensory, pyramidal, and cerebellar signs, as well as the presence of a cold paresis are common features of HD regardless of the type of muscular atrophy.…”

The radiological and electrophysiological characteristics of Hirayama disease with proximal involvement: A retrospective study

“…However, increased understanding of the disease has led to the recognition that patients could experience amyotrophy of the proximal muscles in the upper limbs. Some studies have included patients with proximal symptoms ( 9 , 17 ). Patients with proximal symptoms have been considered in the development of new diagnostic criteria and a new clinical classification system ( 1 , 18 ).…”

“…Therefore, strict criteria for the diagnosis of HD with proximal involvement are needed to prevent misdiagnosis and potential negative outcomes. Some criteria have been defined ( 9 , 10 ), but controlled studies and synthesis of results across studies are lacking.…”