Lower Motor Syndrome Limited to the Upper Extremities with a Snake-eyes Appearance on the Cervical Cord

Dear Editor, We present a patient with lower motor neuron syndrome who exhibited the characteristic “snake-eyes” appearance on magnetic resonance imaging (MRI). The patient was a 27-year-old male who presented with a chief complaint of slowly progressive weakness, clumsiness, and wasting of the muscles in both hands that started 8 years ago. He reported difficulty gripping objects. The patient denied any history of preceding trauma or injury to the affected hand or neck region or a history of poliomyelitis. The parents of the patient had second-degree consanguinity. There was no neurological disease in the family. Neurological examination revealed bilateral wasting of the thenar and hypothenar muscles, as well as wasting of the forearm muscles, and fasciculations in the left arm, with tremulous movements in both hands [Figure 1]. He had slightly asymmetric weakness in the upper extremities, which was distal and left dominant, without any sensory signs. Deep tendon reflexes were hyperactive in all four extremities. Plantar reflexes showed an indifferent response, and the ankle clonus test showed a bilateral positive response. The patient did not have any other neurological deficits or symptoms, and there was no gynecomastia.Figure 1: Thenar, hypothenar, and forearm atrophies of the upper extremitiesAn MRI of the spinal cord was performed, which revealed bilateral intramedullary T2 hyperintensity giving a “snake-eyes” appearance in the bilateral cervical anterior horns in the transverse section [Figure 2]. Flexion imaging showed no displacement of the dorsal dura.Figure 2: The cervical T2-weighted MRI showed a “snake-eye” appearance in the anterior horns in the axial section on the left (thin arrows). A linear hyperintense lesion was detected in the sagittal section in the middle (thick arrow). MRI at maximum flexion of the cervical spine did not show any abnormalities. The peri- and epidural spaces were of normal width on the right. MRI: Magnetic resonance imagingNerve conduction studies were also performed and showed normal amplitudes and velocities of the median, ulnar, tibial, peroneal, and sural nerves with no evidence of conduction block or temporal dispersion. Needle electromyography (EMG) was performed on the proximal and distal muscles of each limb as well as the tongue, which revealed chronic neurogenic changes in the C7–C8 and T1 myotomes. Abnormal spontaneous activity was detected in the bilateral dorsal interossei muscles. The cranial MRI was normal. Blood tests, including metabolic parameters, CK level, HIV, hepatitis, syphilis serology, and vasculitic and tumor markers, were negative. In addition, DNA analysis for Kennedy’s disease, polymerase chain reaction analysis in the C9ORF72 and SOD1 genes, and whole-exome sequencing (performed at the Koc University Neurodegeneration Research Laboratory) were also negative. The patient declined cerebrospinal fluid examination. Based on the patient’s clinical presentation and imaging findings, a lower motor neuron syndrome restricted to the upper extremities with a “snake-eyes” appearance on MRI was diagnosed. During the 3-year follow-up, the patient’s symptoms did not deteriorate, and he did not develop any symptoms of amyotrophic lateral sclerosis (ALS). The patient was referred to physical therapy and rehabilitation to help maintain muscle strength and function. DISCUSSION The patient showed a slowly progressive muscle weakness and atrophy of the bilateral, distal upper extremities with a relatively benign prognosis. Although distal amyotrophy in the upper extremities is a hallmark feature of Hirayama disease in young adults, we did not see a typical radiological sign of dynamic compression of the spinal cord as in Hirayama disease. EMG features were not suggestive of ALS or inflammatory polyneuropathy. The insidious onset of symptoms without bladder dysfunction, absence of systemic symptoms, and weight loss was atypical for spinal cord ischemia or paraneoplastic syndrome. This case highlights the importance of recognizing the “snake-eyes” or “owl-eyes” appearance on MRI as a characteristic finding in lower motor neuron syndrome with a benign prognosis. Microcirculatory disturbances in the anterior horns and venous congestion might be considered regarding the pathomechanism.[1] Mechanical factors such as repetitive traumas from neck flexion and extension or strenuous physical activity may lead to vascular insufficiency.[2] This “snake-eyes” appearance is not specific to any one particular disease, and it can be seen in a variety of conditions that affect the lower motor neurons. This feature is observed in conditions such as spinal muscular atrophy and other similar motor neuron diseases. It is also observed in patients with cervical cord compression due to herniated discs or spinal cord tumors or anterior spinal artery ischemia, and intoxication.[2–5] In addition, a case in which cobalt toxicity was found responsible for the etiology was reported in a patient who experienced progressive upper extremity weakness 5 years after the cobalt-chromium prosthesis was implanted for the hip, and a snake-eye appearance was found on his cervical MRI (most likeyl Hirayama disease).[6] Therefore, clinical examination, extensive laboratory tests (infectious, endocrine, neoplastic, metabolic, immunological markers, even toxicological parameters, if necessary), nerve conduction studies, and genetic tests may be required to diagnose the underlying condition with the “snake-eye” appearance on MRI. Furthermore, the spinal cord MRI is particularly sensitive to movement artifacts and partial volume effects due to the surrounding cerebrospinal fluid. Meeting the necessary technical MRI requirements can help better identify the snake-eyes sign and diagnose this benign entity.[7] This case draws attention as a possible atypical Hirayama disease due to bilateral upper extremity weakness, detection of the Babinski sign, snake-eye appearance on the transverse section of the cervical spinal MRI, and normal flexion MRI. There is no validated treatment; however, the condition is usually treated with physical therapy and rehabilitation to help maintain muscle strength and function.[8] In treatment, neck stabilization with a collar may be preferred to reduce cervical motion and prevent venous ischemia.[2,9] Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.