Monomelic Amyotrophy (Hirayama Disease) With Upper Motor Neuron Signs: A Case Report.
10.5535/arm.2015.39.1.122
- Author:
Seung Don YOO
1
;
Hee Sang KIM
;
Dong Hwan YUN
;
Dong Hwan KIM
;
Jinmann CHON
;
Seung Ah LEE
;
Sung Yong LEE
;
Yoo Jin HAN
Author Information
1. Department of Physical Medicine and Rehabilitation, Kyung Hee University School of Medicine, Seoul, Korea. stylistlsy@gmail.com
- Publication Type:Case Report
- Keywords:
Monomelic amyotrophy;
Pyramidal signs;
Biological assays
- MeSH:
Adolescent;
Atrophy;
Biological Assay;
Denervation;
Diagnostic Errors;
Extremities;
Humans;
Lower Extremity;
Magnetic Resonance Imaging;
Male;
Motor Neurons*;
Muscles;
Neck;
Neurologic Examination;
Shoulder;
Spinal Cord Diseases;
Spinal Muscular Atrophies of Childhood;
Upper Extremity
- From:Annals of Rehabilitation Medicine
2015;39(1):122-127
- CountryRepublic of Korea
- Language:English
-
Abstract:
Monomelic amyotrophy (MMA), also known as Hirayama disease, is a sporadic juvenile muscular atrophy in the distal upper extremities. This disorder rarely involves proximal upper extremities and presents minimal sensory symptoms with no upper motor neuron (UMN) signs. It is caused by anterior displacement of the posterior dural sac and compression of the cervical cord during neck flexion. An 18-year-old boy visited our clinic with a 5-year history of left upper extremity pain and slowly progressive weakness affecting the left shoulder. Atrophy was present in the left supraspinatus and infraspinatus. On neurological examination, positive UMN signs were evident in both upper and lower extremities. Electrodiagnostic study showed root lesion involving the fifth to seventh cervical segment of the cord with chronic and ongoing denervation in the fifth and sixth cervical segment innervated muscles. Cervical magnetic resonance imaging (MRI) showed asymmetric cord atrophy apparent in the left side and intramedullary high signal intensity along the fourth to sixth cervical vertebral levels. With neck flexion, cervical MRI revealed anterior displacement of posterior dural sac, which results in the cord compression of those segments. The mechanisms of myelopathy in our patient seem to be same as that of MMA. We report a MMA patient involving proximal limb with UMN signs in biomechanical concerns and discuss clinical importance of cervical MRI with neck flexion. The case highlights that clinical variation might cause misdiagnosis.
