Anterior spinal artery syndrome

Abstract

Sirs: The anterior spinal artery syndrome (ASAS) is a rare ischemia disorder of the spinal cord [2]. Magnetic resonance imaging (MRI) may confirm the clinical diagnosis but does not show the infarct area acutely in the majority of typical ASAS cases [2]. Therefore, it has been recommended that a search is made for vertebral body infarcts to increase the diagnostic yield of the MRI [3]. As the vascular territory of the anterior spinal artery covers the anterior horn area, subsequent degeneration of motoneurons may be detected by electromyography (EMG). Although anecdotal EMG findings in ASAS have been reported especially in leg or arm muscles [1, 4, 5], EMG use is exceptional for confirming the diagnosis. Here we report 5 patients with ASAS diagnosed in our hospital between 1999 and 2001 that was confirmed by EMG, but in only 2 of them by at least 2 careful MRI investigations. The EMG was performed 2 to 4 weeks after onset of symptoms by routine technique with concentric needle electrodes (Duoliner, Toennies, Wurzburg, Germany). The spinal muscles were investigated for pathological spontaneous activity (PSA) in all patients. Fibrillation potentials and positive sharp waves were accepted as PSA. Patient 1. An 84-year-old woman presented with a flaccid paraparesis after spinal anesthesia for a leftsided knee endoprosthesis operation. The legs could hardly be moved against gravity. Tendon reflexes were absent in both legs, the left patellar jerk could not be tested. The plantar response was extensor on the right and query extensor on the left. Sensory functions could not reliably be tested owing to a mild dementia. She had bladder and bowel incontinence. ASAS was suspected. MRI investigations of the brain 9 days after surgery and of the thoracic spinal cord 7, 17 and 37 days postictal were normal. The EMG showed PSA in each segment from T-9 to L1 on each side. In several segments below and above, no PSA could be detected. Bowel incontinence improved within several days, while the bladder incontinence persisted. With time a mild spasticity developed while the leg weakness showed only minor improvement. Clinical data from this and a further 4 female patients with ASAS are summarised in Table 1. In case 5 the unusual extent of the spinal cord ischemia on clinical presentation and with MRI (Fig. 1) may be due to an anomalously large vascular territory of the anterior spinal artery. A venous outflow obstruction or other cause could also not be ruled out completely. In only 1 further case was the diagnosis confirmed by a follow-up MRI that was planned with the spinal EMG results. Vertebral body inLETTER TO THE EDITORS