CASE OF THE MONTH ABSTRACT: We describe a 53-year-old Caucasian woman with a 19-year history of an evolving amyotrophy confined to her dominant right arm and hand. Although this atypical case of a late-onset monomelic amyotrophy in some respects mimics Hirayama disease or O’Sullivan–McLeod syndrome, it does not conform precisely with either of those disorders. We compare this individual’s difficulties and clinical temporal profile to other disorders con- sidered in the differential diagnoses with regard to her evolving clinical setting. Muscle Nerve 37: 115–119, 2008 LATE-ONSET MONOMELIC AMYOTROPHY IN A CAUCASIAN WOMAN DHARMESH R. PATEL, MD, 1 LAURIE KNEPPER, MD, 2 and H. ROYDEN JONES, Jr., MD 1 1 Department of Neurology, Lahey Clinic, 41 Mall Road, Burlington, Massachusetts 01805, USA 2 Department of Neurology, Berkshire Medical Center, Pittsfield, Massachusetts, USA Accepted 23 March 2007 We describe an atypical case of a late-onset monomelic amyotrophy that clinically has some sim- ilarities with Hirayama disease (juvenile muscular atrophy of distal upper extremity) or O’Sullivan– McLeod syndrome. However, in contrast to the typ- ical adolescent male with Hirayama disease, who is a native of the western Pacific Rim nations, particu- larly Japan, our patient is a now 53-year-old Cauca- sian woman whose neurologic symptoms began dur- ing her mid-30s, a feature that is also not seen in the O’Sullivan–McLeod syndrome. To date, her disor- der has defied specific diagnosis; however, we are struck by the 19-year course with no progression to other limbs or the bulbar region, the multiple non- diagnostic studies, and previous unsuccessful thera- peutic interventions initially for a possible anterior interosseous neuropathy and later for multifocal mo- tor neuropathy (MMN). CASE REPORT This 53-year-old right-handed woman, a now dis- abled artist of English–Scottish ancestry, presented to us with a weak right hand and forearm. Her initial symptoms began in 1988 at the age of 34 years. These primarily consisted of right thenar fascicula- tions. One year later, during pregnancy, she experi- enced the gradual onset of weakness, with difficulty in holding her paint brushes in her right hand sec- ondary to dysfunction of her right flexor pollicis longus and flexor digitorum profundus of the index finger. An anterior interosseous syndrome was ini- tially diagnosed at another hospital. Subsequently, an exploration of this nerve at the antecubital fossa failed to define a specific entrapment site or other anatomic lesion. Within 4 years of onset she could no longer hold a paintbrush and had to retire as an artist. She then had an ingravescent course; in 1999 she sought a further opinion at another facility. An electromyogram (EMG) was performed; the patient was told that her current difficulties repre- sented sequellae to the previous median nerve ex- plorative surgery. Subsequently, she was evaluated by a neuromuscular specialist who considered a possi- ble diagnosis of a spinal muscular atrophy variant. In 2001 she sought an opinion at a neighboring qua- ternary neurologic center. A diagnosis of possible MMN was considered in 2002. However, despite careful motor nerve conduction studies including Erb’s point and cervical root stimulation, no defini- tive conduction block was identified. Anti-GM1 anti- bodies were not present. Despite this, she com- menced monthly empirical treatment with 20 g of intravenous immunoglobulin (IVIg) for possible MMN. Although she initially thought that she might be experiencing a subtle transient improvement in Abbreviations: ADM, abductor digiti minimi; ALS, amyotrophic lateral scle- rosis; APB, abductor pollicis brevis; CMAP, compound muscle action poten- tial; EMG, electromyogram; FDI, first dorsal interosseous; IVIg, intravenous immunoglobulin; MMN, multifocal motor neuropathy; MUP, motor unit poten- tial; SMA, spinal muscular atrophy; SMN, survival motor neuron; SNAP, sen- sory nerve action potential Key words: amyotrophy; Hirayama disease; monomelic; O’Sullivan–McLeod syndrome; spinal muscular atrophy Correspondence to: H. Royden Jones; e-mail: [email protected] © 2007 Wiley Periodicals, Inc. Published online 8 May 2007 in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/mus.20811 Late-Onset Monomelic Amyotrophy MUSCLE & NERVE January 2008 115
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