Effect of transcutaneous electrical nerve stimulation (TENS) on central nervous system amplification of somatosensory input.

The effect of transcutaneous electrical nerve stimulation (TENS) on the central nervous system amplification process was investigated focusing on the dorsal column-medial lemniscal pathway, because the dorsal column nucleus was recently shown to receive multiple sources of sensory information, including pain. Short latency somatosensory evoked potentials (SSEPs) were recorded in ten healthy normal volunteers. Amplitude changes in each SSEP component (the N9 brachial plexus potential, the P14 potential that originates from the cervicomedullary junction, spinal N13/P13 generated by the cervical dorsal horn and the cortical N20/P25 potential) were studied at stimulus strengths ranging from the threshold (40% maximum stimulus) to 2.5 times the threshold (maximum). The findings suggest that sensory amplification begins at the P14 generator source near the cuneate nucleus. There was no statistically significant difference in sensory amplification between P14 and cortical N20/P25, indicating that the cuneate nucleus is the main site of the central amplifying process. When TENS was applied to the palm distal to the median nerve stimulation used for SSEP, cortical N20/P25 amplification disappeared, evidence that TENS suppresses the central amplification phenomenon, most probably at the level of the cuneate nucleus.

Clival chordoma associated with pathological laughter. Case report.

The case of a 40-year-old man with a clival chordoma who presented with symptoms of pathological laughter and left sixth cranial nerve paresis is reported. Laughing and talking during sleep were noted on polygraphic and videotape recordings of nocturnal sleep. Selective disorganization of sleep was observed, with laughing facial expressions and a lack of muscular atonia. The tumor developed in the prepontine cistern, compressing the pontomesencephalic structures backward and involving the upper clivus and the left cavernous sinus. No recurrence of laughter attacks were noted after total removal of the tumor. The sleep patterns observed were similar to those of experimental animals with lesions of the peri-alpha locus ceruleus. The importance of uncontrolled laughter as a sign of a ventral brain-stem mass is emphasized.

The effects of hyperthermia on the spinal cord.

This study was conducted to obtain information about the critical temperature of the spinal cord in hyperthermia produced by radiofrequency waves applied to the spine. The first component of the spinal cord evoked potential was analyzed as an indicator of spinal cord function. The spinal cords were heated by radiofrequency waves to a maximum of 47 degrees C momentarily or for 30 minutes. The temperatures were measured with a thermosensor in the epidural space. In momentary heating, the reductions in amplitude were almost parallel with the increases in temperature. In maintained heating for 30 minutes, at 44 degrees C and below, the amplitudes decreased by one-quarter to three-quarters of the control value in the first 5 minutes and recovered to over three-quarters of the control value in 30 minutes. The amplitudes returned to almost the control value after restoration of normal spinal cord temperatures. At 45 degrees C and above, however, the amplitudes were prominently reduced or disappeared in the first 5 minutes and remained depressed during the remainder of the heating. On normalizing the temperature, the amplitudes did not return to the control value. These results suggest that 44 degrees C in the epidural space is the highest tolerable temperature for normal spinal cord function.

Atlas hypoplasia manifesting as myelopathy in a child--case report.

A 14-year-old Japanese boy presented with myelopathy due to atlas hypoplasia with complete posterior arch. Decompressive laminectomy of the atlas produced good neurological recovery, and follow-up T2-weighted magnetic resonance imaging showed disappearance of spinal cord edema. Congenital atlas stenosis may be symptomatic even in children, with no accompanying cervical spondylotic change. Such cases have previously occurred only in Asian adults. A radiological study of the patient's brother showed median cleft formation of the posterior arch of atlas, indicative of a wide spectrum of atlas anomalies and a possible genetic relationship between these anomalies.

Delayed, transient neurological deterioration after mild head injury--case report.

A 16-year-old boy presented with delayed, transient neurological deterioration 18 days after mild head injury. Left hemiparesis and left homonymous hemianopsia appeared after right frontal contusional and mild subdural hematomas subsided. Neuroimaging examinations including cerebral angiography, magnetic resonance imaging, and single photon emission computed tomography showed vasodilation and hyperemia in the right cerebral hemisphere. The present case is not typical of acute "juvenile head trauma syndrome," but may represent a possible pathophysiology of the delayed type of transient neurological deterioration after mild head injury.

Hyperbaric oxygen therapy adjunctive to mild hypertensive hypervolemia for symptomatic vasospasm.

The efficacy of hyperbaric oxygen (HBO) therapy was evaluated retrospectively in 43 patients who developed symptomatic vasospasm following acute aneurysm surgery. HBO therapy was given as an adjunct to mild hypertensive hypervolemia in 24 patients. Before HBO therapy, 17 patients had no infarct (Group 1), and seven had infarcts (Group 2) caused by vasospasm. A further 19 patients received mild hypertensive hypervolemia alone (Group 3). Cerebral infarcts developed in four Group 1 and 12 Group 3 patients. A good outcome 1 month after surgery was achieved by 13 Group 1 (76%), one Group 2, and seven Group 3 patients (37%). Fifteen of the 24 patients who received HBO therapy responded to HBO exposure, and 12 responding patients (80%) had a good outcome. During HBO exposure, electroencephalographic improvements were all accompanied by neurological improvements. There were no complications related to HBO therapy. HBO therapy adjunctive to mild hypertensive hypervolemia is helpful in preventing cerebral infarction associated with symptomatic vasospasm.

Effects of night work on the cognitive function in young and elderly subjects with specific reference to the auditory P300.

To estimate the effects of night work on the human cognitive function, P300 event related potentials (ERPs) evoked with an auditory "oddball" paradigm were recorded for 17 nurses (mean age 27.4 +/- 6.1 years; range 21-41 years) for 3 epochs; after a night of work, after a day of work and on a holiday, and for 12 elderly security guards (mean age 62.8 +/- 2.2 years; range 60-67 years) for 2 epochs; after a night of work and on a holiday. The Stress Arousal Check List (SACL) was used for all the subjects just prior to the P300 ERP recording to determine the extent of stress and the arousal grades. Fourteen of the nurses were in their twenties (mean age 24.9 +/- 2.6 years; range 21-29 years), and 3 (39.0 +/- 2.6) were older (36, 40 and 41 years). The 14 nurses were classed as the young group. All the security guards were classed as the elderly group. In the young group, the stress grade scores increased significantly (P < 0.05) and the arousal grades decreased significantly (P < 0.01) after night work as compared to the holiday values. Although statistically not significant, the amplitude of the P300 component tended to decrease after night work, whereas the latency was very stable for these 2 epochs. The P300 latencies of the 3 older nurses were as stable as those of the young group, but their amplitudes were significantly reduced after night work as compared with the holiday amplitudes (P < 0.05). In contrast, the 12 elderly security guards showed no statistically significant changes in the scores for the stress and arousal grades between the 2 epochs, after night work and holiday. Latency prolongation however, was statistically significant (P < 0.01) after night work. The P300 amplitudes for many of the elderly security guards also tended to decrease after night work, but were not statistically significant. The P300 amplitude is considered to reflect the amount of attentional resources and the latency to reflect the time needed for the cognitive process, indicating that the elderly security guards experiences slowing of the cognitive process in night work. Our results suggest that the effect of night work on the cognitive function is greater for elderly than for young workers. We conclude that P300 can be used to evaluate changes in the human cognitive function produced by night or rotating shift work and that the results provide useful information with which to plan shift schedules on the basis of worker age.

Clinical application of paraspinal somatosensory evoked potentials (PS-SEPs) for the diagnosis of spinal cord lesion.

To evaluate the clinical utility of somatosensory evoked potentials elicited by stimulation of the paraspinal region (PS-SEPs), waveform characteristics and scalp topography were studied in 23 normal controls. PS-SEPs were recorded in 22 patients with spinal lesions, and the relation between the abnormal PS-SEPs and clinico-radiological findings was investigated. 1) The normal control study showed clear waveforms on the scalp elicited by stimulation of the paraspinal region from C7 to the L2 spinous process level, with both bilateral and unilateral stimulation. The latency of PS-SEPs was gradually decreased when stimulation was moved in the caudo-rostral direction. 2) The normal range of spinal conduction time and conduction velocity was wide. The conduction velocity resulting from stimulation of the lumbar region tended to be slower than that from stimulation of the thoracic region, perhaps due to the difference in the length of the peripheral cutaneous nerves. 3) There was no correlation between the height and the latency of PS-SEPs. 4) Amplitudes of PS-SEPs after unilateral stimulation of the C7 and Th5 spinous levels were larger on the scalp contralateral to the side of stimulation. These findings were similar to SEPs elicited by median nerve stimulation. There was no significant amplitude laterality of PS-SEPs when the Th10 and L2 spinous levels were stimulated. Posterior tibial nerve SEPs showed a larger amplitude at the scalp ipsilateral to the side of stimulation than at the contralateral side. All these findings suggest that the cortical generator sites of PS-SEPs elicited by C7 and Th5 stimulation are located near the hand area, and those from Th10 and L2 stimulation are between the hand and the foot area. 5) Unilateral stimulation disclosed a clear laterality of sensory disturbance that was obscure when only bilateral stimulation was employed. PS-SEPs showed a high degree of abnormality when the patient had deep sensory disturbance. Generally, abnormal PS-SEPs were found caudal to the clinical sensory level, and a few cases showed abnormal PS-SEPs rostral to the sensory level. The latter might indicate that PS-SEPs detected subclinical sensory disturbance. It was therefore concluded that PS-SEPs are a useful tool for the objective evaluation of sensory disturbance, especially in cases of thoracic lesion, because conventional SEP studies, utilizing non-cephalic references do not provide clear identification of abnormal sensory levels along the thoracic spinal cord.

Origin of subcortical somatosensory evoked potentials in response to posterior tibial nerve stimulation in humans.

To identify the origin of short latency somatosensory evoked potentials (SSEPs) to posterior tibial nerve stimulation, direct recordings were made from the cervical cord, the ventricular system and the frontal subcortex during 8 neurosurgical operations. The origin of each component of SSEPs was also studied in 7 selected patients with various lesions in the central nervous system. In addition, SSEPs to median nerve stimulation were investigated in 4 of 8 surgical cases and all 7 cases of the lesion study group. Bilateral posterior tibial nerve stimulation in 10 normal subjects showed spinal N28 on the skin of the posterior neck and far-field P30 and N33 components followed by a cortical P38 component at the scalp. Direct recordings made to the mid-brain through the medulla oblongata showed a negative potential with gradually increasing latency. The peak of the negativity in the vicinity of the dorsal column nucleus showed almost the same latency as that of the scalp far-field P30, and positivity with a stationary peak was found above the dorsal column nucleus. Above the mid-pons, there was a stationary negativity with no latency shift, showing the same peak latency as that of scalp N33. The spatiotemporal distributions of P30 and N33 to posterior tibial nerve stimulation were analogous to those of P14 and N18 by median nerve stimulation. Transesophageal and direct cervical cord recordings showed that the spinal N13 phase to median nerve stimulation was reversed between the dorsal and ventral sides of the cervical cord. No such reversal occurred for the spinal N28 potential. Clinical lesion studies showed that changes in P30 and P14, and in N33 and N18 correlated with one another: that is, 1) prolongation of latency of N33 was also observed for N18; 2) absence of P30 was paralleled by the absence of P14. These data suggest that spinal N28 originates from ascending activity such as a dorsal column volley, and scalp P30 comes from activity near the dorsal column nucleus, which is similar to the P14 component of median nerve stimulation. The origin of N33 is thought to be similar to N18 from median nerve stimulation, which originates from brainstem activity below the thalamus.

[A case of hematoma in cisterna magna after mild head injury].

An 18-year-old man suffered severe neck pain, signs of meningeal irritation, and dysesthesia of his left breast and left arm after mild head injury incurred in a traffic accident. On the next day, magnetic resonance imaging(MRI) revealed a hematoma in the cisterna magna, and it extended into the posterior spinal subdural space. Eight days after admission, MRI demonstrated the hematoma on the right posterior aspect of the spinal cord at the level of craniovertebral junction. These MRI findings suggested a ruptured bridging dorsal vein from the spinal cord to the occipital or marginal sinus. The usefulness of MRI for diagnosis of localized hematoma around the craniovertebral junction and the mechanism of this hemorrhage are discussed.

[Unusual MR findings of Wernicke encephalopathy with cortical involvement].

We report a 48-year-old chronic alcoholic man, who developed consciousness disturbance, oculomotor paresis, and flaccid tetraplegia. His dietary habit was very poor since one month prior to the present admission and he was drinking alcoholic beverage. On admission on April 19, 1999, he showed disturbance of consciousness, tetraparesis without sensory disturbance, gaze paresis, and vertical nystagmus on downward gaze. His blood thiamine level was 12 ng/ml (normal range: 23.8-45.9). MRI demonstrated symmetric hyperintense lesions in the motor and premotor cortices bilaterally, in addition to other changes indicating Wernicke's encephalopathy. His motor weakness and oculomotor disturbance improved after treatment with intravenous thiamine. His cortical MRI also normalized. We believe that his cortical abnormality was responsible for his motor paresis and this is an unusual and unique finding for Wernicke's encephalopathy.

P30 and N33 of posterior tibial nerve SSEPs are analogous to P14 and N18 of median nerve SSEPs.

Generator sources of far-field P30 and N33 components produced by posterior tibial nerve stimulation were compared with those of the P14 and N18 components of median nerve stimulated somatosensory evoked potentials. Intracranial spatio-temporal distributions of P30 and N33 were similar to those of the P14 and N18 obtained by median nerve stimulation. In clinical cases, the changes in P30 and N33 were correlated with those in P14 and N18, indicative that P30 and N33 are derived from activities similar to those that produce P14 and N18.

[Evaluation of neuro-Behçet disease with 99mTc-HMPAO brain SPECT: comparison with MR imaging].

The purpose of this study was to evaluate the brain perfusion of neuro-Behçet disease using 99mTc-HMPAO. In total, nine patients (7 men and 2 women) were evaluated. Seven were in the chronic phase, one was acute and the other was subacute. The results of perfusion study were compared with the MRI findings. The findings of chronic-phase neuro-Behçet disease were as follows: 99mTc-HMPAO showed hypoperfusion of the cerebellum in 3, brain stem in 5, and cerebral cortex in 4 patients. Moreover, asymmetry of the basal ganglia and thalamus was seen in 4 cases with 99mTc-HMPAO. MRI showed atrophy of the cerebellum in 4, brain stem in 5 and cerebral cortex in 2 patients. One acute patient showed a perfusion defect with 99mTc-HMPAO that was consistent with the vasculitis shown with MRI. In the remaining subacute patient, perfusion defect was demonstrated with 99mTc-HMPAO, consistent with the infarction shown with MRI. It is concluded that brain perfusion scintigraphy is useful to evaluate the brain blood flow of neuro-Behçet disease.