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Hirayama disease (HD) is a rare disorder characterized by insidious asymmetric neurogenic atrophy primarily involving the upper extremities. HD most commonly affects adolescent males and has a favorable prognosis for arrest of progression. Electrodiagnostic (EDX) studies show chronic denervation changes in the distal upper extremity muscles. A cervical spine MRI in neck flexion may reveal compression of the cervical ventral spinal cord. We report clinical, EDX, and MRI findings in two cases of HD. The first case involved a 15-year-old male with a six-month history of progressive weakness, wasting, and tremulous movements of the left hand without pain or paresthesia. A physical exam revealed marked wasting of the left intrinsic hand muscles with polyminimyoclonus. Needle electromyography (EMG) revealed fasciculations (simultaneous with the polyminimyoclonus) while at rest and recruitment of 1-2 large polyphasic units in the left C8, T1, and, to a lesser extent, the C7 distribution. A T2-weighted flexion cervical spine MRI revealed narrowing and anterior displacement of the posterior dura of the cervical cord, leading to cord compression at C5-6 and C6-7. At last contact 11 years following symptom initiation, the patient continued to complain of profound weakness of the left hand without pain or numbness. The second case involved a 17-year-old male who was found to have wasting of the intrinsic muscles of the non-dominant left hand on a routine physical examination. The left first dorsal interosseus, abductor digiti minimi, abductor pollicis brevis, and extensor pollicis longus muscles were found to be clinically weak. Polyminimyoclonus involving all fingers of the left hand was also observed. A needle EMG demonstrated fasciculations with large amplitudes and wide duration motor unit potentials in the left C8, T1, and, to a lesser extent, C7 distribution. An ultrasound study showed frequent fasciculations in the left intrinsic hand muscles and the distal forearm muscles simultaneously with the polyminimyoclonus. A T2-weighted cervical spine MRI scan in the flexed sagittal position revealed anterior displacement of the dura and an enlarged epidural space from C4-C7. At last follow-up 11 months later, the findings were unchanged. The EDX studies and cervical MRI findings were consistent with HD in both cases. The role of EDX studies and cervical spine flexion MRI in diagnosing HD and the correlation between polyminimyoclonus and fasciculations are highlighted., Competing Interests: Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. The University of Louisville Institutional Review Board issued approval 22.1095. The University of Louisville Institutional Review Board determined that this study was exempt according to 45 CFR 46.101(b) under Category 4. Written consent was obtained from the patients in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Shields et al.)

Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuropathy. Duplication of the peripheral myelin protein-22 ( PMP22 ) gene is the most frequent genetic abnormality in CMT disease. Although rare compared to PMP22 gene mutations, many different myelin protein zero ( MPZ ) gene mutations have been described in patients with CMT disease.  MPZ  gene mutations are known to cause hereditary neuropathies with heterogenous phenotypes ranging from early-onset severe demyelinating to adult-onset axonal forms. MPZ, the major protein component of peripheral nerve myelin, is important for myelin compaction. We report a family in which a mother and her son, both with adult-onset CMT disease, showed a newly described mutation p.Glu37Lys of the MPZ gene. The clinical features of the mother provided insight into the progression of the disease over decades, while features in the early stage of the disease could be studied in the son. Clinical, electrodiagnostic, and sonographic findings are described in the early and late stages of the disease. The MPZ gene mutation p.Glu37Lys is associated with clinical features of a progressive axonal type of adult-onset CMT disease., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Iyer et al.)

Background A reverse total shoulder arthroplasty (RTSA) is often recommended for rotator cuff pathology and may be associated with a myriad of complications, including prosthetic instability, infection, humeral problems, and glenoid loosening. Neurological injuries following an RTSA are infrequent and are usually related to brachial plexus or proximal nerve injury in the affected arm. Iatrogenic ulnar nerve neuropathy is exceedingly rare. Aims This study describes the clinical and electrodiagnostic (EDX) features of 18 patients with ulnar nerve neuropathy complicating RTSA. Materials and methods All patients underwent EDX studies, and 14 had an ultrasound (US) study. Results All patients complained of numbness, tingling, hyperalgesia, and/or allodynia in the distribution of the ulnar nerve. Eight (44%) patients reported hand weakness, and one (6%) noted wasting of the intrinsic hand muscles. Decreased pinprick sensation in the ulnar nerve distribution was detected in all patients. Seventeen (94%) patients had weakness of the ulnar nerve-innervated intrinsic hand muscles. All patients had focal slowing of the motor conduction of the ulnar nerve across the elbow. Sensory potentials were either absent or of a low amplitude over the digital and/or dorsal cutaneous branch of the ulnar nerve in all patients. Twelve (86%) patients showed an increase in the cross-sectional area (CSA) of the ulnar nerve at the elbow; six (43%) had a hypoechoic ulnar nerve. Ulnar nerve neuropathy was confirmed at the elbow in all 18 patients. Of the 14 (78%) patients who underwent surgical intervention for ulnar nerve neuropathy following an RTSA, only four had complete symptom resolution. Conclusions Surgeons should be cognizant of ulnar nerve neuropathy as a potential complication of an RTSA and take precautions to avoid damage to the ulnar nerve intraoperatively. EDX and US studies should be performed to confirm and assess the site and severity of the injury., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Shields et al.)