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제목 Importance of Sufficient Neck Flexion during MRI in the Diagnosis of Hirayama Disease 소속 Keimyung University Dong-san Hospital, Department of Rehabilitation Medicine1 저자 Du Hwan Kim1†, Jae Wook Lee1* Introduction
Hirayama disease (HD) is considered as dynamic compressive myelopathy usually unilaterally affecting the distal upper limb in young men. Because of atypical manifestations on HD, it is difficult to rule out other mimicking disorders. Confirmation of a dynamic change of the dorsal epidural space on MRI during neck flexion is essential for diagnosis of HD. However, insufficient or no cervical flexion during MRI may lead to misdiagnosis or delayed diagnosis of HD. We report two cases of HD that were initially confused with other diseases due to a suboptimal position of the neck or the absence of cervical flexion during MRI.
Case 1.
An 18-year-old male presented with a 5-year history of right hand weakness with hand muscle atrophy. He was diagnosed with posterior interosseous nerve syndrome (PINS) and recieved exploratory surgery in another hospital. However his weakness did not improve, so he visited another hospital. Because of a high suspicion of HD, routine cervical MRI in a neck flexion position was performed but did not reveal cord atrophy or dynamic compression of the spinal cord (Fig. 1A & B). MRI of the upper arm revealed hyperintensity and swelling of the median and ulnar nerves. Thus, he was tentatively diagnosed with neuralgic amyotrophy at that hospital. He visited our clinic for a second opinion on his weakness. We conducted electrophysiologic study and the results of that suggested HD rather than PINS or neuralgic amyotrophy (Table 1). Hence, we repeated contrast-enhanced cervical MRI with sufficient flexion, which showed detachment of the dural sac from the lamina and spinal cord compression by engorgement of posterior epidural venous plexus (Fig. 1C).
Case 2.
A 16-year-old male with a 3-month history of progressive right wrist extensor weakness visited our hospital. Cervical MRI showed disc protrusion at C5–6 and C6–7 (Fig. 2A), whereas results of electrophysiologic study were suggested with radial neuropathy (Table 1). His weakness thereafter progressed to intrinsic hand muscle involvement over 3 weeks. Signs of sensory deficit or root irritation were absent. Considering these clinical manifestations, we suspected HD rather than cervical radiculopathy or PINS. Cervical MRI with neck flexion was repeated. The detachment of the dural sac from the lamina was suspicious (Fig. 2B). Cervical MRI with more flexed position showed an obvious anterior shift of the lower cervical cord and widening of the dorsal epidural space (Fig. 2C).
Discussion
There is no consensus on the optimum extent of neck flexion during cervical MRI to ensure the correct diagnosis, and neck-flexion MRI is not routinely performed in juvenile patients with distal upper limb weakness if a physician does not suspect HD or if neutral MRI does not reveal cord atrophy. Dynamic cervical MRI including a fully flexed position is absolutely recommended in juvenile distal upper limb weakness.
File.1: Hirayama F1.jpgFig. 1. (A) Cervical MRI revealed no signal change of the spinal cord in a neutral position. (B) In a suboptimal neck flexion, did not show dural detachment. (C) In a fully flexion, demonstrated a crescent-shaped enlarged posterior epidural space.File.2: Hirayama F3.jpgFig. 2. (A) Cervical MRI in a neutral position showed disc protrusion at C5–6 and C6–7. (B) In a neck flexion, revealed suspicious dural detachment. (C) In a fully flexion, demonstrated obvious widening of the dorsal epidural space.File.3: table1.JPGTable 1. The results of peripheral nerve conduction studies.
