Median nerve somatosensory evoked potentials recorded with cephalic and noncephalic references in central and peripheral nervous system lesions.

Somatosensory evoked potentials (SSEP) to electrical stimulation of the median nerve by using cephalic and noncephalic references were studied to detect the generator sources of short latency evoked potentials in 29 patients with cerebral, brainstem, spinal and peripheral nerve lesions. Patients were divided into six groups according to the localization of their lesions: group 1: cortical and subcortical lesions, group 2: basal ganglion lesions, group 3: pons and mesencephalon lesions, group 4: diffuse cerebral lesions, group 5: cervical cord lesions, group 6: brachial plexus lesions. Potentials were recorded using cephalic and noncephalic references after median nerve stimulation. Evidence obtained from patients suggested the following origins for these short latency SSEPs: P9 may arise in brachial plexus, P11 in dorsal basal ganglions or dorsal column, P13 and P14 in the nucleus cuneatus and lemniscal pathways, N16 in subthalamic structures and most likely mid and lower pons, N18 from the thalamus and thalamocortical tract, and N20 from primary somatosensory cortex.

Unusual late responses in a patient with an Arnold-Chiari malformation.

We studied a young man with spastic right hemiparesis, in whom supramaximal stimulation of the left posterior tibial nerve produced toe movements of the both feet and associated late responses in the flexor hallucis brevis muscle bilaterally. These findings indicate that, in this patient, there are central connections between peripheral afferents and contralateral alpha-motor neurons. It may be that such connections are normally present but that they are too weak in normal subjects to produce firing of the alpha-motor neurons by themselves. If so, the loss of cortical inhibition in our patient may have allowed these connections to produce movement.

Order effects in response times of parkinsonian patients and normal controls.

Response latencies were measured in 6 parkinsonian patients and 6 normal subjects in a choice reaction task requiring the discrimination of two different tones with different probabilities of occurrence (frequent and rare). Response latency was measured from stimulus onset to onset of electromyographic activity in the responding muscle. Rare-tone responses were separated on the basis of the number of frequent tones intervening between the rare tone of interest and the immediately preceding rare tone (defined as rare-tone position). Frequent-tone responses were separated by the number of consecutive frequent tones occurring either before or after a rare tone (defined as frequent-tone position). Rare- and frequent-tone position had a significant impact on response latency. Both patients and controls had the shortest response latencies to rare tones when four frequent tones (the median interval for these experiments) intervened. Similarly, the response latency to frequent tones increased at approximately this same median interval after a rare event for both patients and controls. These findings suggest that normal controls utilize probability information about both global probabilities and their immediate past experience in order to modify upcoming responses. Our findings also indicate that patients with Parkinson's disease do not differ from normal subjects in this regard, and thus that even subtle attributes of preprogramming are not affected in Parkinson's disease, despite suggestions by others to the contrary.

Simple and choice reaction time in Parkinson's disease.

Reaction-times were evaluated in 6 parkinsonian patients and 6 normal control subjects using a simple reaction task and 3 choice reaction tasks of differing complexity. Reaction-times were measured as the time from stimulus onset to the onset of electromyographic activity in the responding muscle. Reaction-time was significantly delayed in patients compared to controls in all tasks, but to a greater extent in the more difficult tasks. The relative magnitude of the change, however, was only 4% in the simple reaction task and 8% in the more difficult choice tasks. These results suggest that the deficit in Parkinson's disease is unlikely to represent a defect in preprogramming as suggested by some investigators. Instead, our results indicate a disturbance in the cerebral processing of the auditory stimuli after their occurrence and prior to the initiation of motor activity.

Migrainous stroke causing bilateral anterior cerebral artery territory infarction.

A 38-year-old man developed bilateral anterior cerebral artery territory infarction during the course of a migraine. Magnetic resonance imaging showed bilateral ischemic lesions involving the cortex of the paramedian region of the frontal and parietal lobes, more prominent on the right. Cerebral angiography was normal. To our knowledge, this is the first report of bilateral anterior cerebral artery territory infarction from migraine.

Acetyl salicylic acid improves somatosensory evoked potentials in streptozotocin-diabetic rats.

The effects of acetyl salicyclic acid (ASA) on somatosensory evoked potentials (SEP) and neural levels of thiobarbituric acid reactive substances (TBARS), products of lipid peroxidation, were studied in streptozotocin-diabetic rats. ASA (100 mg/kg, in rat chow) was given to diabetic rats (n = 8) after the induction of diabetes for 16 weeks. ASA-treated normal control rats (n = 8), untreated diabetic rats (n = 8) and normal control rats (n = 8) were used for comparison. At the 8 weeks, SEP latency in diabetic group (15.4 +/- 0.5 ms) was significantly longer than that in normal control group (10.0 +/- 0.8 ms, P < 0.05). When compared to levels in diabetic control group, ASA shortened SEP latency significantly (12.7 +/- 0.1 ms; P < 0.05). This effect of ASA was significant in all three measurements from week 8 to 16 (P < 0.05 vs. diabetic control group). Neural TBARS level in diabetic control group (60.1 +/- 2.2 nmol/g) was significantly, higher than that in normal control group (28.5 +/- 3.6 nmol/g, P < 0.05). When compared to levels in diabetic control group, ASA depressed TBARS level significantly (41.5 +/- 12 nmol/g; P < 0.05). TBARS level in ASA-treated diabetic group (27.2 +/- 5.7 nmol/g) was comparable with that in normal control group (NS). These results suggest that ASA has beneficial effect on diabetic neuropathy and this effect may be related in part with prevention of lipid peroxidation.

Mirror movements associated with cervical meningocele: case report.

A patient with mirror movements associated with cervical meningocele has been presented in this report. The MRI showed normal cerebrum and cervical meningocele, and an anomaly at the posterior to the cervical spinal cord-medulla junction. Unilateral transcranial magnetic stimulation evoked bilateral responses at similar latencies on the thenar muscles which are quite different from those observed in normal subjects. This case adds another etiological cause to the mirror movements.

Cerebral accompaniments to simple and choice reaction tasks in Parkinson's disease.

In order to clarify the nature and basis of the delayed reaction time that occurs in Parkinson's disease, we measured reaction times and cerebral responses in six parkinsonian patients and six normal age-matched control subjects. Each participated in one simple reaction task and three choice reaction tasks of different complexity. The reaction times were delayed in the parkinsonian patients in all conditions but especially in the more difficult choice tasks. In addition, the cerebral responses showed delayed latencies of the N1, N2, and P3 components of the event-related cerebral potential. These findings are similar to the changes that we observed previously in patients with both Parkinson's disease and dementia, and suggest that bradyphrenia may account, in part, for the slowing of response time in Parkinson's disease.

Radiological follow-up in encapsulated intracerebral hematoma mimicking intratumoural bleeding.

Chronic encapsulated intracerebral hematoma, which is usually seen in young, normotensive patients, is rare, but has been reported with increasing frequency in recent years. In this report, we have presented a case of encapsulated intracerebral hematoma mimicking intratumoural bleeding with its whole natural radiological progression. A 55 year-old man developed a progressive neurological deficit one month after hospitalisation due to spontaneous intracerebral hemorrhage. Cranial CT and MR demonstrated a ring-shaped hemorrhagic lesion with mass effect and perifocal edema. After 15 months, there was marked improvement in clinical findings, and imaging techniques showed marked resorption of the mass. Radiological findings of spontaneous resolution of the encapsulated intracerebral hematoma are described for the first time in the reported case. Encapsulated intracerebral hematoma can present much like a brain tumour and should be considered in the differential diagnosis of other hemorrhagic space-occupying lesions.

Traumatic basilar artery dissection causing locked-in syndrome.

We report on a patient with traumatic dissection limited to the basilar artery causing a locked-in syndrome. Magnetic resonance imaging (MRI) showed infarction of the basis pontis and a high signal intensity ring surrounding the central lumen of the basilar artery. Vertebral angiography revealed a double lumen within the basilar artery, consistent with a dissection. MRI and angiography are complementary to each other, and we consider both to be necessary for accurate diagnosis. Because MRI is less invasive than angiography, MR examinations should be performed before angiography for screening.

Free musculofasciocutaneous medial plantar flap for reconstruction of thenar defects.

Functional reconstruction of thenar skin defects complicated by muscle loss is possible by transfer of a medial plantar flap with the underlying abductor hallucis muscle. Three patients with severe flexion-adduction contractures of the thumb due to gunshot injuries were reconstructed by using this musculofasciocutaneous flap. At surgery, after release of the skin contractures, all dysfunctional fibrotic muscles were excised. A medial plantar flap and the abductor hallucis muscle were dissected together; the motor branch of the abductor hallucis was preserved by intraneural dissection and sutured to the thenar motor branch of the median nerve. The muscle ends were sutured across the defects of the thenar muscles. All flaps survived without any loss at follow-up of 6-9 months. The flaps adapted to the thenar region completely by providing sufficient thenar bulk and a good skin colour match with palmar skin. Electromyography of the transferred muscle showed an interference pattern with an amplitude of about 200 mV in two cases and 100 mV in one case. Clinically, these findings were supported by voluntary opposition of the thumbs with good strength.