Hirayama disease: electric shocks and muscle weakness
A 25-year-old man presented with a 5-year history of an insidious, progressive weakness in his right hand. Despite being right-handed, he had recently become reliant on his left hand to carry out tasks needing manual dexterity. Clinical examination showed muscular atrophy without fasciculations of the first dorsal interosseous muscle and weakness of both the thenar and hypothenar muscles of the right hand; he also had atrophy but no fasciculation of the lumbrical and interosseous muscles. He complained of bilateral, electric shock-like sensations throughout his body when we examined the range of movements of his neck—Lhermitte's sign. Laboratory investigations showed a serum B12 concentration of 648 pg/mL (normal range 174–878) and the serum panel for heavy metal toxicity—including arsenic, mercury, and lead—was negative. Investigations for rheumatoid arthritis—including antinuclear antibody and rheumatoid factor (less than 14 IU/mL)—were within the normal ranges and his erythrocyte sedimentation rate was normal at 2 mm/h.

An MRI of the patient's brain showed no abnormalities; however, an MRI of his cervical spine showed myelomalacia of the spinal cord but no other features that might give a clue as to the underlying cause of his problems (figure). The association of the patient's electric shock-like sensations prompted us to do a dynamic cervical spine MRI study with the neck in positions of flexion and extension: MRI showed that the spinal cord was being compressed—most noticeably at the level of the fifth cervical vertebral body—and that the dorsal epidural space was abnormally expanding while in a flexed position (figure). Such radiographic findings are pathognomonic of Hirayama disease and so clinched the diagnosis.

To prevent further neurological injury, a two-level anterior cervical spine fusion at C4/C5 and C5/C6 using synthetic interbody grafts between the vertebral bodies after removal of the intervertebral disc material; these were secured with a titanium plate from C4 to C6. A further dynamic cervical spine MRI done 6 weeks after the operation showed that the spinal cord was no longer being compressed when the patient flexed his neck (figure). Dexterity in his right hand had subjectively improved at follow-up 6 months later.

Source: https://www.thelancet.com/article/S0140-6736(19)31784-2/fulltext
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M●●●●●●a B●●●i General Medicine
Medicine is really awesome!!
Sep 17, 2019Like1