Introduction:

Juvenile Muscular Atrophy of the distal upper extremity (JMADUE) is caused by a forward displacement of the posterior dura during cervical flexion and was first described by Hirayama et al in 1959.  Young male patients at a mean age of around 17 years are primarily affected . It presents with changes in the extensor and flexor muscles of the fingers and wrist. A few patients also show slight symptoms of hypesthesia in localized area of the hand. For diagnosis and subsequent treatment a dynamic MRI in flexion of the cervical spine is essential. Typically the condition progresses slowly and resolves within 5 years. 

The aim of this systematic review and meta-analysis was to document the number of reported cases, the necessity of dynamic MRI of the cervical spine and the subsequent treatment in JMADUE.

Methods:

A systematic Review was conducted on 31 Aug 21. The Pubmed/ Medbase, Cochrane, Google, Embase and Ovid database were searched following the PRISMA guidelines. The search terms were (Hirayama) AND ((disease) OR (syndrome)) and a total of 851 abstracts were screened. Studies presenting data on Hirayama disease with more than 7 cases were included where a dynamic MRI was performed for diagnosis. A total of 226 studies reporting 3,539 patients were eligible for screening including 122 case reports (54.0%) and 42 case series (18.6%), leaving 62 retrospective studies for analysis. 

Results:

Within the 62 studies, 3,273 patients suffering from JMADUE were reported. The mean age was 20.1±1.71 years and predominantly males  in 61.8% were identified. On MRI, the “snake eyes” appearance of the spinal cord was present in 8.2% and the typical time between onset of symptoms and diagnosis was 37.6±16.6 months. Treatments for the condition ranged from observation, the application of a cervical collar, and anterior cervical discectomy and fusion (ACDF). Although the inverventions are suggested to prevent progressive muscular weakness in an early stage, there is no substantial evidence that any of them are superior to observation. 

Conclusion:

The number of case reports and case series being published recently on JMADUE and the delay in diagnosis from initial presentation of symptoms show that this condition may be underdiagnosed in a variety of cases. Current guidelines suggest an MRI or CT scan in the supine position may be helpful. However, these may miss functional causes of spinal stenosis such as a dilated venous plexus in the posterior epidural space. This study shows the necessity of dynamic MRIs in flexion and the development of new guidelines especially in adolescents to identify functional spinal and/ or foraminal stenosis for a prompt diagnosis and subsequent treatment.