Hirayama Disease: The Role of the Neuroradiologist to Confirm the Diagnosis and Correlation with Electromyography

Hirayama disease, or juvenile spinal muscular atrophy of the distal upper limb, is a rare myelopathy due to a cervical spinal cord compression injury with asymmetric growth.[1,2] Symptoms begin insidiously and consist of muscle weakness and atrophy in one hand and forearm, usually giving the appearance of oblique amyotrophy, without sensory loss.[2] A 15-year-old patient developed weakness in the upper limbs with asymmetry, mainly affecting the left side. He had difficulty in extending the fingers, more importantly in three and four fingers [Figure 1] and atrophy in the extensor and flexor muscles in the left forearm associated with reduced bicipital and styloradial reflexes. There were no other complaints. The nerve conduction study showed compound muscle action potential of the radial nerve with reduced amplitudes. The electromyography observed signs of active denervation with rarefied recruitment, worse on the left, in myotomes C6 to T1 [Figure 2]. Magnetic resonance imaging (MRI) demonstrated low cervical cord C5–C7 myelomalacia with atrophic changes, subtle anterior displacement of the posterior dura and enlargement of posterolateral epidural space and laminodural distance on the right [Figure 3]. After hyperflexion, there was a significant increase of the enlargement of anterior displacement of the posterior dura and distended epidural venous plexus enhancement in posterolateral epidural space on the right, features compatible with Hirayama's disease [Figure 4].Figure 1: Images of the upper limbs in pronation and supination demonstrating atrophy of the extensor (a) and flexor muscles (b) and of the thenar region, with sparing the hypothenar. Difficulty in extending the fingers (c). There was no change in sensitivityFigure 2: Electroneuromyography of the upper limbs. Signs compatible with active denervation and chronic reinnervation in the flexor carpi radialis muscle (C6 and mainly C7 – a); denervation in activity and chronic reinnervation in the triceps muscle (C7 – b); chronic reinnervation in the index extensor muscle (C6 and C7 – c)Figure 3: 3.0 TESLA MRI cervical spine with sagittal T1 (a), T2-weighted (b), and axial T2-weighted gradient (c and d) echo images in a neutral position. Low cervical cord C5–7 myelomalacia with atrophic changes, subtle anterior displacement of the posterior dura and enlargement of posterolateral epidural space and laminodural distance on the right (arrows)Figure 4: 3.0 TESLA MRI cervical spine high-resolution sagittal T2 (a), postcontrast T1-weighted (b), axial T1 (c), axial FIESTA (d), and axial postcontrast T1-weighted (e) images after hyperflexion maneuver. Significant increase of the enlargement of anterior displacement of the posterior dura and distended epidural venous plexus enhancement in posterolateral epidural space on the right (arrows)Currently, there is no treatment and consensus to reverse the feeling of weakness in the limbs[1,3], although the early diagnosis and early intervention can halt the progression of the disease or even stabilize it.[1,3] Declaration of patient consent Full and detailed consent from the patient/guardian has been taken. The patient's identity has been adequately anonymized. If anything related to the patient's identity is shown, adequate consent has been taken from the patient/relative/guardian. The journal will not be responsible for any medico-legal issues arising out of issues related to patient's identity or any other issues arising from the public display of the video. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.