Abstract
Hirayama disease (HD) is characterized by the juvenile onset of unilateral or asymmetric weakness and amyotrophy of the hand and ulnar forearm and is most common in males in Asia. A perception of compliance with previous standards of diagnosis and treatment appears to be challenged, so the review is to update on HD. First, based on existing theory, the factors related to HD includes, (1) cervical cord compression during cervical flexion, (2) immunological factors, and (3) other musculoskeletal dynamic factors. Then, we review the clinical manifestations: typically, (1) distal weakness and wasting in one or both upper extremities, (2) insidious onset and initial progression for 3–5 years, (3) coarse tremors in the fingers, (4) cold paralysis, and (5) absence of objective sensory loss; and atypically, (1) positive pyramidal signs, (2) atrophy of the muscles of the proximal upper extremity, (3) long progression, and (4) sensory deficits. Next, updated manifestations of imaging are reviewed, (1) asymmetric spinal cord flattening, and localized lower cervical spinal cord atrophy, (2) loss of attachment between the posterior dural sac and the subjacent lamina, (3) forward displacement of the posterior wall of the cervical dural sac, (4) intramedullary high signal intensity in the anterior horn cells on T2-weighted imaging, and (5) straight alignment or kyphosis of cervical spine. Thus, the main manifestations of eletrophysiological examinations in HD include segmental neurogenic damages of anterior horn cells or anterior roots of the spinal nerve located in the lower cervical spinal cord, without disorder of the sensory nerves. In addition, definite HD needs three-dimensional diagnostic framework above, while probable HD needs to exclude other diseases via “clinical manifestations” and “electrophysiological examinations”. Finally, the main purpose of treatment is to avoid neck flexion. Cervical collar is the first-line treatment for HD, while several surgical methods are available and have achieved satisfactory results. This review aimed to improve the awareness of HD in clinicians to enable early diagnosis and treatment, which will enable patients to achieve a better prognosis.
Highlights
Hirayama disease (HD), which is referred to as juvenile muscular atrophy of the distal upper extremities or monomelic amyotrophy, is a special neurological disorder that was first reported by a Japanese neurologist, Keizo Hirayama [1]
Atrophy of the Muscles of the Proximal Upper Extremity The compression associated with HD is usually restricted to the lower cervical spinal cord, mainly at the C7-T1 level; the atrophy observed in most patients is located in the distal upper extremity
These are [1] asymmetric cord flattening and localized lower cervical cord atrophy due to compression by the tight posterior dural wall, mostly at the C4 to C7 level; [2] abnormal cervical curvature; [3] loss of attachment between the posterior dural sac and the subjacent lamina [59]; [4] noncompressed intramedullary high signal intensity on T2-weighted imaging (T2WI), a sign that can be caused by ischemia or necrosis of anterior horn cells (AHCs)
Summary
Hirayama disease (HD), which is referred to as juvenile muscular atrophy of the distal upper extremities or monomelic amyotrophy, is a special neurological disorder that was first reported by a Japanese neurologist, Keizo Hirayama [1]. There are three mechanisms through which the venous plexus engorges: negative pressure in the posterior epidural space due to anterior displacement of the dura; impaired venous drainage in the jugular veins during cervical flexion and consequent diversion of flow toward the posterior epidural plexus; and shifting of blood to the posterior epidural compartment from the compressed anterior venous plexus [44] Both autopsies and neuropathologic studies have demonstrated that major lesions of HD occur primarily in locations such as the cervical anterior horn and the ventral roots. Wang et al found that the neutral and flexion Cobb angles in HD patients decreased from C2/3 to C5/6 but increased at C6/7; this may be another cause of the observed dynamic instability [51]
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