Neurological complications of ankylosing spondylitis: neurophysiological assessment

Abstract

Studies examined the neurological involvement of ankylosing spondylitis (AS) are limited. This study aimed to assess the frequency of myelopathy, radiculopathy and myopathy in AS correlating them to the clinical, radiological and laboratory parameters. Included were 24 patients with AS. Axial status was assessed using bath ankylosing spondylitis metrology index (BASMI). Patients underwent (a) standard cervical and lumbar spine and sacroiliac joint radiography, (b) somatosensory (SSEP) and magnetic motor (MEP) evoked potentials of upper and lower limbs, (c) electromyography (EMG) of trapezius and supraspinatus muscles. Patients' mean age and duration of illness were 36 and 5.99 years. Bath ankylosing spondylitis metrology index mean score was 4.6. Twenty-five percent (n = 6) of patients had neurological manifestations, 8.3% of them had myelopathy and 16.7% had radiculopathy. Ossification of the posterior (OPLL) and anterior (OALL) longitudinal ligaments were found in 8.3% (n = 2) and 4.2% (n = 1). About 70.8% (n = 17) had >or=1 neurophysiological test abnormalities. Twelve patients (50%) had SSEP abnormalities, seven had prolonged central conduction time (CCT) of median and/or ulnar nerves suggesting cervical myelopathy. Six had delayed peripheral or root latencies at Erb's or interpeak latency (Erb's-C5) suggesting radiculopathy. Motor evoked potentials was abnormal in 54% (n = 13). Twelve (50%) and five (20.8%) patients had abnormal MEP of upper limbs and lower limbs, respectively. About 50% (n = 12) had myopathic features of trapezius and supraspinatus muscles. Only 8.3% (n = 2) had neuropathic features. We concluded that subclinical neurological complications are frequent in AS compared to clinically manifest complications. Somatosensory evoked potential and MEP are useful to identify AS patients prone to develop neurological complications.

Symptomatic noncompressive motoromyelopathy presents as early manifestation in ankylosing spondylitis

“…Unfortunately, cord injury is only concerned in case of spinal fracture and is barely mentioned without vertebral disorder. Nevertheless, variable magnitude of spinal blocking has already been demonstrated in 63-71% of AS patients without spinal fracture [18,19], implicating the fact that subclinical spinal cord injury is underestimated in AS. On the other hand, AS may be overlooked in symptomatic NCM when typical skeletal symptom is absent or minimal, especially in women who tend to manifest skeletal symptoms at neck, shoulder, upper chest, or peripheral joint instead of lower spinal column [20] as our patients.…”

Thoracic spinal cord herniation in a patient with long-standing ankylosing spondylitis

“…Nearly all patients presented with a symptom of sensory or reflex loss [3]. In AS, the erosive inflammatory condition has preference toward erosion of openings where tendons and ligaments insert into bone, and then it causes the body's biochemistry to attempt to fill in the defect with new bone growth [25]. From above, inflammation not only increases the risk of neurological deficit of AS, but also increases the risk for SCH.…”

Somatosensory Evoked Potential Findings in Ankylosing Spondylitis

“…Though infrequent, neurological complications related with this disease have been reported in the literature. Nervous system involvement, more of the central nervous system (multiple sclerosis, cauda equina syndrome, focal epilepsy, vertebrobasilar insufficiency) and less of the peripheral nerves, is known in AS [2][3][4].…”

“…Also there may be other late neurological complications such as arachnoid diverticuli within the lumbar column resulting in cauda equina syndrome [1][2][3][4][5][6]. Conversely, in some recent reports, an association with AS and multiple sclerosis (MS) has also been reported [1,[6][7][8].…”