Object: The diagnosis of tethered cord syndrome (TCS) remains difficult, and the decision to operate is even more complex. The objective of this study was to examine how detailed examination of neurophysiological test results can affect the diagnosis for patients undergoing a surgical cord release. Methods: Patients undergoing tethered spinal cord releases were matched by age and sex with control patients undergoing scoliosis correction in the absence of spinal cord pathology. The latency and width of the P37 peak of the posterior tibial nerve somatosensory evoked potential (SSEP) and the motor evoked potential (MEP) latencies were examined. Immediate changes as a result of the surgical procedure were reported. Results: The width of the P37 response differed significantly between TCS and control patients and changed significantly during the surgical procedure. Nonsignificant trends were seen in SSEP and MEP latencies. Conclusions: The width of the P37 response may be a useful marker for TCS and may play a role in presurgical decision making.
Journal Of Clinical Neurophysiology: Official Publication Of The American Electroencephalographic Society [J Clin Neurophysiol] 2013 Aug; Vol. 30 (4), pp. 382-5.
Adolescent, Anesthesia statistics numerical data, Child, Electric Stimulation instrumentation, Electric Stimulation methods, Electroencephalography, Extremities physiology, Humans, Motor Cortex physiology, Motor Neurons physiology, Retrospective Studies, Scoliosis etiology, Scoliosis surgery, Spinal Fusion methods, Spinal Muscular Atrophies of Childhood complications, Evoked Potentials, Motor physiology, Extremities physiopathology, Motor Cortex physiopathology, and Spinal Muscular Atrophies of Childhood physiopathology
Spinal muscular atrophy is a progressive condition in which movement is gradually lost as a result of the loss of spinal motor neurons. Individuals with this condition may require surgical correction of a secondary scoliosis. Motor evoked potentials were recorded using transcranial electrical stimulation in four such individuals undergoing surgery. All the patients were nonambulatory and in wheelchairs. Motor evoked potentials were recordable in both upper and lower limb muscles, with similar stimulation parameters to control subjects undergoing surgery for idiopathic scoliosis. The amplitudes of the motor evoked potentials were similar to those in control subjects, although the latencies were shorter reflective of the smaller stature of the spinal muscular atrophy patients. The relative preservation of the motor evoked potentials despite the patients' poor voluntary motor control suggests that there is a selective preservation of the motor neurons mediating the motor evoked potential in spinal muscular atrophy and a maintenance of the conduction velocities of the corticospinal tract.
Norton JA, Thompson AK, Chan KM, Wilman A, and Stein RB
Clinical Neurophysiology: Official Journal Of The International Federation Of Clinical Neurophysiology [Clin Neurophysiol] 2008 Jan; Vol. 119 (1), pp. 80-7. Date of Electronic Publication: 2007 Nov 26.
Aged, Brain Mapping, Cerebral Palsy pathology, Electric Stimulation, Electromyography, Functional Laterality, Humans, Magnetic Resonance Imaging, Male, Transcranial Magnetic Stimulation, Cerebral Palsy physiopathology, Evoked Potentials, Motor physiology, and Movement physiology
Objective: To determine the mechanisms underlying the mirroring of distal movements in both upper and lower limbs present in one individual from birth. Methods: Transcranial magnetic stimulation (TMS), magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), voluntary and reflexly evoked electromyograms (EMG) and force measurements were used to obtain information about the motor pathways responsible for the mirror movements. Results: MRI showed a significant loss of brain tissue from one hemisphere and fMRI indicated a significant functional reorganization had taken place. An obligatory mirroring of voluntary movement on the sound side occurs on the affected side, but some independent movement can be produced on the affected side, if enabled by weak contractions on the sound side. TMS mapping revealed bilateral projections from one hemisphere and virtually absent projections from the primary motor cortex of the other hemisphere. Spinal reflexes were restricted to the stimulated side. Transcortical reflexes were evoked bilaterally from the sound side, but not from the affected side. Conclusions: The physiological and imaging data are consistent with a mirroring from the intact motor cortex via the supplementary motor area. Significance: Mirror movements in this individual represent a major cortical reorganization and a partial solution to the neonatal loss of substantial amounts of brain tissue.
Experimental Brain Research [Exp Brain Res] 2007 Sep; Vol. 182 (2), pp. 281-7. Date of Electronic Publication: 2007 Aug 24.
Adult, Analysis of Variance, Electromyography methods, Evoked Potentials, Motor radiation effects, Female, Humans, Male, Motor Cortex radiation effects, Muscle, Skeletal physiology, Pyramidal Tracts anatomy histology, Pyramidal Tracts radiation effects, Reaction Time, Time Factors, Electric Stimulation methods, Evoked Potentials, Motor physiology, Leg innervation, Motor Cortex physiology, Pyramidal Tracts physiology, and Transcranial Magnetic Stimulation
Transcranial direct current stimulation (tDCS) of the human motor cortex at an intensity of 1 mA has been shown to be efficacious in increasing (via anodal tDCS) or decreasing (via cathodal tDCS) the excitability of corticospinal projections to muscles of the hand. In this study, we examined whether tDCS at currents of 2 mA could effect similar changes in the excitability of deeper cortical structures that innervate muscles of the lower leg. Similar to the hand area, 10 min of stimulation with the anode over the leg area of the motor cortex increased the excitability of corticospinal tract projections to the tibialis anterior (TA) muscle, as reflected by an increase in the amplitude of the motor evoked potentials (MEPs) evoked by transcranial magnetic stimulation. MEP amplitudes recorded at rest and during a background contraction were increased following anodal tDCS and remained elevated at 60 min compared to baseline values by 59 and 35%, respectively. However, in contrast to the hand, hyperpolarizing cathodal stimulation at equivalent currents had minimal effect on the amplitude of the MEPs recorded at rest or during background contraction of the TA muscle. These results suggest that it is more difficult to suppress the excitability of the leg motor cortex with cathodal tDCS than the hand area of the motor cortex.