A 21 year old young male presented with complaints of neck pain and weakness of right hand associated with numbness for four years, which was insidious in onset and gradually progressive. He had difficulty in writing, buttoning and unbuttoning clothes, glass holding and eating. His neck pain increased on bending the neck forward and on looking downwards. He also noticed thinning of right hand and tremors and tremulousness of right hand fingers. There was no history suggestive of weakness of proximal muscles of arm and lower limbs, and bladder or bowel disturbances. There was no history of trauma.
Examination revealed no neurocutaneous markers, ulcers, or thickened nerves. Cranial nerve examination was normal. Motor examination revealed wasting [Figures 1 and 2] and weakness of intrinsic muscles of right hand. Deep tendon jerks and superficial reflex were normal. Sensory examination revealed hypoesthesia in right C6 dermatome. Coarse tremors were seen in the right-hand fingers. No cerebellar signs were noticed. Pulse and blood pressure in both upper limbs was normal.
His dynamic magnetic resonance imaging (MRI) cervical spine revealed plaque-like area in the posterior epidural space, most prominent at C5 and C6 levels associated flow voids, resulting in compression on posterior surface of the spinal cord [Figure 3A and B]. There was no cervical cord compression observed in neutral and extension position imaging [Figures 4 and 5]. Thinning of spinal cord at C5-C6 levels, with associated T2 hyperintense myelomalacic changes were seen [Figures 6 and 7]. Contrast image [Figure 8] revealed homogenously enhancing epidural space from C3 to C7.
Surgical and conservative options were discussed with the patient and relatives; they opted for surgery as his neck pain was bothering him much and as a student he could not write. Therefore, anterior cervical discectomy and fixation fusion using PEEK cage screws at C5/6 [Figure 9] was done; intraoperatively, there was a soft disc and multiple dilated epidural vessels were seen on lateral aspects of thecal sac. Postoperatively, there was no neck pain. Philadelphia cervical collar was applied postoperatively.
On follow-up, his neck pain resolved and he had no further deterioration in power or increased atrophy in the affected intrinsic muscles of hand. At 5-month follow up, his hand grip showed 60% improvement.
Etiopathogenesis of Hirayama disease (HD) is not known; there are two theories that suggest dynamic compression.
One theory suggests increased laxity of the dorsal dura, allowing anterior shift of the spinal cord during repeated neck flexion, which produces subclinical cervical cord trauma and micro-ischemia to the anterior horn of the cervical spinal cord. This leads to degeneration and asymmetric lower cervical cord thinning within the C5–T1 segments. This laxity may be caused by a growth imbalance in the vertebral column and dura mater, particularly noted during growth spurts in a young individual in the second decade of life. As growth stops, posterior dura mater displacement decreases, causing a plateau of the disease process.
A second theory suggests that the posterior longitudinal ligament has two cellular matrixes: one with fine elastic ligament and the other with larger elastic ligaments. These ligaments designed to secure the posterior dura mater are unequally dispersed, allowing only part of the cord to have anterior displacement and accounting for the unilateral presentation based on decreased elasticity found on some surgical and cadaveric specimens.[1,2,3]
HD has insidious onset, unilateral or asymmetric weakness of small muscles of the hand. The weakness usually involves both extensors and flexors of fingers. The tremulousness of hand on extension of the fingers is often seen. About two-thirds of patients do not worsen clinically after about 5 years of disease onset.
Routine cervical spine MRI will show lower cervical cord atrophy, hyperintensity on T2-weighted imaging in the anterior part of cord in the absence of medullary compression, and loss of normal cervical curvature.[5,6] However, dynamic MRI of the cervical spine (neutral, flexion, and extension) is the imaging modality of choice for the diagnosis of HD. Loss of attachment of the posterior dura mater in the neutral position is considered one of the most valuable signs of HD. Flexion MRI of the cervical spine shows anterior displacement of posterior wall of dura mater and appearance of epidural flow voids which enhance on gadolinium contrast injection. Neutral position cervical MRI showing asymmetrical cord atrophy and anterior shift of posterior dural wall along with flow voids in the posterior epidural compartment is highly predictive in HD.[5,6,7]
Treatment of HD is targeted to prevent further flexion injury of cervical cord by inadvertently repeated neck flexion. Hence, many authorities recommend the use of hard cervical collar to prevent any further flexion injury of the cervical cord. The benefits are more likely in patients who have been diagnosed early and have milder cord atrophy.[6,8] Nondecompression and nonfusion surgery was successful and achieved satisfactory results in HD patients.[9,10]
In our case, surgical and conservative options were discussed with the patient and relatives; they opted for surgery as his neck pain was bothering him much, even after wearing cervical collar and as a student he could not write. Therefore, we performed anterior cervical discectomy and fixation fusion (ACDF) using PEEK cage screws at C5–C6 level. Immediately after surgery, his neck pain subsided and at 5 months follow-up he showed 60% right hand grip improvement.
ACDF could also be considered as an effective treatment option for the treatment of HD.
Although HD is said to be a self-limiting disease, in a young person early diagnosis and early surgical intervention can hamper the progression of disease and prevents disability.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent form. In the form the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understand that his name and initial will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.
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Conflicts of interest
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