Value of Needle Electromyography for the Diagnosis of Amyotrophic Lateral Sclerosis

ABSTRACT

BACKGROUND AND PURPOSE: For the diagnosis of amyotrophic lateral sclerosis(ALS), symptoms and signs of upper motor neuron(UMN) and lower motor neuron(LMN) involvement should be confirmed. The electromyography(EMG) studies are known to be essential for the demonstration of LMN involvement. The authors assessed the value of the EMG in the diagnosis of ALS. METHODS: The authors collected 51 patients (MF=3120, age51.9?12.0 years) who were diagnosed and followed up at Seoul National University Hospital from 1994 to 1996. Diagnosis of ALS was based on the El Escorial diagnostic criteria. They were classified to be definite in 5, probable in 23, and possible in 23. On view of the affected area of onset, they consisted of 12 bulbar and 39 spinal form of ALS. The needle EMG studies were performed in limb, thoracic paraspinal and tongue muscles. RESULTS: Of 51 cases, it was possible to demonstrate widespread denervations at the initial needle EMG tests in 46(90.2%); 5 of 5 definite, 21 of 23 probable, and 20 of 23 possible ALS. Among 30 spinal form ALS without bulbar symptoms, the initial EMG evaluation showed the widespread denervation processes in three limbs in 13(43.3%) and in two limbs in 17(56.7%). Of 17 patients with denervation in only two limbs, the thoracic paraspinal and tongue muscles were found to be involved in 7 and 5 cases, respectively. The other 5, who initially showed abnormal EMG in limited muscles without abnormal EMG finding in thoracic paraspinal and tongue muscles, were confirmed to have ALS by the clinical and EMG follow-up. Nine patients of spinal onset ALS with bulbar symptoms and 12 patients of bulbar onset showed widespread denervation features at the tongue and limb muscles. In 6 ALS cases, difficult to be differentiated from spondylotic myeloradiculopathy, the abnormal EMG features in thoracic paraspinal and bulbar muscle were helpful to diagnose ALS. CONCLUSION: The authors could diagnose ALS in most cases(90.2%) at the time of initial EMG evaluation. The needle EMG study with the regular follow-up is useful to diagnose ALS. Moreover, the needle EMG study on thoracic paraspinal and tongue muscle is much helpful to differentiate ALS from spondylotic myeloradiculpathy.