Clinical Spectrum of Hirayama Disease in Tertiary Care Hospital

Abstract

INTRODUCTION Juvenile muscular atrophy of the unilateral upper limb localized to hand and forearm was first reported independently in 1959 from Tokyo by Keizo Hirayama [et. al] and Takagi, Okabe. Benign monomelic amyotrophy (BMA) is considered a less common form of motor neuron disease of as yet unknown cause. In view of the first such case being reported by Keizo Hirayama, this disease is now being referred to as Hirayama disease. The clinical features of Hirayama disease were summarized based on previous studies (15-19). This disease affects people in their teenage or early second decade, it preferentially affects the males (male to female ratio = 20:1). There have been rare case reports of Familial occurrence, six pairs have been reported till date in over 300 case reports from Japan. Description of patients presenting with similar complaints has been reported differently by authors. Each author had given a different name to describe the disease they were reporting as the etiology of this disease is largely unknown. This confusion in disease categorization led to the emergence of multiple synonyms for this spectrum of clinical syndromes. AIM OF THE STUDY: 1. To study the clinical, nerve conduction and radiological profile of patients diagnosed to have Hirayama disease. OBJECTIVES: 1. To study the clinical profile of Hirayama disease. 2. To study the changes in Nerve conduction study parameters, with respect to median and ulnar f wave study in the neutral position of the neck and flexed position of the neck in patients with Hirayama disease and to compare its significance between the 2 neck position and also with controls. 3. To study the MRI changes in patients with Hirayama disease in neck neutral position and neck flexion position. MATERIALS AND METHODS: Study Design: Retrospective and prospective study. Setting: Government Stanley Medical College and Hospital, Chennai. Study population: All patients with clinical suspicion of HD between Jan 2011 to Jan 2013 were included in the study. Inclusion criteria: 1) All patients with hand muscle wasting for whom the etiology could not be ascertained on standard evaluation for secondary motor neuron disease. 2) Weakness and wasting predominantly in one or both upper limbs. 3) Absence of cranial nerve, sphincter or cerebellar deficits. 4) 5 control subjects, age matched, with no neurological illness, Exclusion criteria: 1) Patients with focal upper limb atrophy and weakness due to focal disease of nerve, muscle, bone, or maldevelopmental diseases. 2) Patients of Hansen’s disease. 3) Patients diagnosed to have traumatic, infectious, vasculitic and metabolic plexopathy or neuropathy with hand wasting. RESULTS: • Males are predominantly affected with M : F = 7 : 1 • 70% of patients have bilateral involvement. • 55% of patients have predominant right hand involvement. • Average age at onset of first symptom is 18.9 years. • Overnight exposure to cold environment induced worsening of weakness was seen in 25% of patients. This phenomenon is seen in patients with disease duration of less than 18 months. • In this study 19% patients had transient sensory disturbance usually associated with phenomenon of cold paresis. • Hirayama disease predominantly involves distal upper limbs, but in this study 35% of patients additionally had proximal upper limb involvement. • In this study brisk DTR was observed in 35% of patients. • Proximal muscle fasciculation was present in 25% of patients. • Ulnar nerve F latency is prolonged and is accentuated significantly in neck flexion. • Median F latency is also prolonged but is not significantly accentuated on neck flexion. CONCLUSION In this study, in addition to the features originally described by Kiezo Hirayama, atypical features such as bilateral involvement, proximal muscle wasting, sensory symptoms, fasciculation and brisk DTR were observed. This study also concludes that in Hirayama disease ulnar nerve conduction studies of mild prolongation of the f wave latency which is accentuated on neck flexion will characterize this disease. This feature can be used as a monitoring parameter and also to objectively record progress during therapy. MRI of the cervical spine in Hirayama disease patients with neck in neutral position is often reported as normal. It is an essential tool to rule out secondary treatable causes of compressive or non compressive myelopathy. Dynamic neck flexion MRI highlights the characteristic features of Hirayama disease. In this study despite the smaller sample size it can be concluded that the presence of atypical features, predominant right hand involvement in young males, ulnar f wave changes and MRI changes are characteristic features and not pathology of the disease. The pathogenesis of Hirayama disease is still an enigma wrapped in a mystery with a possibility of segmental neuronal damage due to mechanical disturbance of integuments, vascular compromise and / or degenerative processes. Hence decompressive procedures are debated. To facilitate preservation of hand function and quick rehabilitation, cervical collar application may be of immense help to patients with` Hirayama disease

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