Robin Gilmore

Evaluation of children and young adults with tethered spinal cord syndrome. Utility of spinal and scalp recorded somatosensory evoked potentials.

The diagnosis of tethered spinal cord syndrome should be considered in young patients with progressive orthopedic deformities, lower extremity weakness, urinary and fecal incontinence, low back pain, or combinations of these symptoms. Myelographic, computed tomographic, and urodynamic studies are useful for establishing a diagnosis, but contribute little to the evaluation of lower extremity sensory function or to the assessment of electrophysiologic impairment of the spinal cord itself. To determine the diagnostic usefulness of the somatosensory evoked potential after posterior tibial nerve stimulation (posterior tibial nerve somatosensory evoked potential) in tethered spinal cord syndrome, 22 consecutive patients with symptoms of tethered spinal cord syndrome (aged 18 months to 22 years) underwent recording of posterior tibial nerve somatosensory evoked potential; results were correlated with clinical, myelographic, and operative findings. In patients with clinical symptoms but no myelographically demonstrable lesions, posterior tibial nerve somatosensory evoked potentials were within normal limits, suggesting normal physiologic function. In patients with myelographically and operatively confirmed tethering dysraphic lesions, posterior tibial nerve somatosensory evoked potential was predictive of the level and laterality of the lesion. Similarly, ranking the severity of neurological impairment and extent of dysraphism at operation, as well as the extent of abnormality of posterior tibial nerve somatosensory evoked potential, revealed a significant (r = 0.81, p less than 0.001) correlation between clinical severity and posterior tibial nerve somatosensory evoked potential abnormalities. Postoperatively, in 8 patients, posterior tibial nerve somatosensory evoked potential also reflected improved function in relation to the level and type of dysraphic lesion present. These findings indicate that posterior tibial nerve somatosensory evoked potential is a sensitive indicator of neurophysiologic status in patients with tethered spinal cord, and is useful for determining the level of the conus medullaris, degree of spinal cord displacement, and severity of neurological impairment associated with this congenital disturbance of neuraxis formation. Recording of posterior tibial nerve somatosensory evoked potential is noninvasive and offers a more sensitive diagnostic tool than the clinical testing of sensation for detection of the development of neurologic deficits in patients with tethered cord syndrome.

Evoked Potentials in the Elderly

Evoked potentials (EPs) provide a quantitative measure of function rather than structure of certain pathways and processes within the nervous system. These systems and processes change with maturation and senescence. There are minimal somatosensory EPs changes after maturation until senescence. There are moderate changes in interpeak latencies, but few changes in the central conduction time (CCT). Brainstem auditory EPs change minimally with aging, with the CCT prolonging by 1–4 ms/year, possibly in a gender-dependent fashion. Latencies of visual EPs prolong by 2–4 ms/decade after age 40 years. The P300 amplitude, latency, and distribution all change with age. An understanding of the characteristics of EPs in aging humans is essential to accurate clinical interpretation of these studies.

Sleep-Disordered Breathing in Möbius Syndrome

Möbius syndrome is a complex neurologic disorder characterized by congenital bilateral facial paralysis associated with lateral gaze paralysis. The syndrome has variable manifestations and several variants, some with somatic stigmata. In 1990, Möbius syndrome is conceptualized as a spectrum of clinical caudal brain-stem signs. Some deficits are manifested by laryngeal paralysis and aspiration. Sleep-disordered breathing syndromes have not been previously reported in association with Möbius syndrome. We report two children with Möbius syndrome and sleep-disordered breathing. Based on known pathologic findings and clinical manifestations, we believe that sleep-disordered breathing may be a common complication of Möbius syndrome and should be sought, since potential outcomes of such complications include serious morbidity. (J Child Neurol 1991;6:73-77).

Review Article: The Use of Somatosensory Evoked Potentials in Infants and Children

Somatosensory evoked potentials (SSEPs) are a useful, reliable means of assessing function of the somatosensory system. Complex maturational changes of the CNS such as synaptogenesis and myelination, as well as body growth, complicate interpretation of SSEPs. An understanding of these factors enhances clinical interpretation in infants and children. (J Child Neurol 1989 ;4 :3-19).

Somatosensory evoked potential testing in infants and children.

Somatosensory evoked potentials (SSEPs) provide the means to assess noninvasively the peripheral and central nervous system in infants and young children. As experienced clinicians know, this is the very system most difficult to adequately evaluate in young children. Physical examination is difficult. SSEPs provide information about function of somatosensory systems not otherwise available. In addition to pathologic states, maturation and sleep produce changes in SSEPs that require careful analysis.