Electrophysiological Changes During Cerebellar Dentatotomy in Cats

Spasticity is a wide variety of motor problems to connote difficulty with coordinated movements, involuntary spasma, rigidity. Abnormal primitive reflexes and hyperactive reflexes. Electrophysiologically, spasticity is represented as the involuntary firing of motor units on a reflex basis at a polysynaptic spinal cord level, associated with interruption of descending cortical pathways. Although many procedures have been tried over the years to combat this spasticity, and the multitude of procedures indicates that none are entirely satisfactory, the reduction in spasticity produced by dentatotomy has been confirmed in many neurological centers. The F-wave is a late response recorded in the electromyography of a muscle following stimulation of its nerve supply. There is evidence that the size of the F-wave is dependent on motor neuron excitability. If such a relationship exists, procedures which are carried out to relieve motor neuron excitability might be expected to change F-wave size and it might therefore be possible to use the F-wave as an objective monitor during stereotactic dentatotomy. We have investigated this possiblity in 10 cats, weighing 2.8 to 3.7kg each. The size of F-wave Amplitude in experimental animals were devided into 2 groups, normal control group values(10 cats, before dentatotomy) and the dentatotomy group values(10 cats after dentatotomy). The F-wave size and F/M ratio were recorded from right tibialis anterior muscle after application of supramaximal stimulation(250 V. 100 mA. 2 Hz. 10 times) on the right peroneal nerve. The results were as follows: 1) The size of M-wave amplitude did not change significantly in experimental models(before dentatotomy, 2805.5+/-1012.3 microV;dentatotomy group, 2555.5+/-725.9 microV, P>0.05). 2) The individual size of F-wave showed a wide variability from each stimulus, which emphasizes the importance of using 0 stimulating responses. The mean value of F-wave amplitude before dentatotomy was 436.5+/-113.2microV. 3) The size of F-wave amplitude was significantly reduced after dentatotomy(before dentatotomy, 436.5+/-113.2microV;after dantatotomy: 212.5+/-49.3microV, P<0.05). The size of F-wave amplitude decreased about 48.6% after dentatotomy. 4) The F/M ratio also significantly reduced after dentatotomy(before dentatotomy, 17.1+/-6.6%;after dentatotomy, 8.5+/-1.2%, P<0.05) and mean reduction was 49.7%. The results demonstrated that the dentatotomy markedly decreased the size of F-wave amplitude in experimental cats and indicated that the monitoring of F-wave amplitude during dentatotomy might be useful as an objective monitor for the relief of spasticity.

2 Cases of Anterior Communicating Artery Aneurysms Associated with Visual Symptoms

Interference with visual pathways is usually not caused by intracranial aneurysms. Aneurysms of the anterior communicating artery rarely produce visual symptoms and signs in spite of their proximity to the visual pathways. The reason may be that these aneurysms rupture and present with subarachnoid hemorrhage before becoming large enough to exert significant pressure on the chiasm or optic nerves. The visual symptoms would be presented as visual field defect or impaired vision. These can be explained as the result of direct compression of the optic pathways, ischemic changes in the visual pathways caused by severe vasospasm after subarachnoid hemorrhage, or intraocular pathology such as retinal hemorrhage. 2 cases of anterior communicating artery aneurysms associated with visual symptoms are presented with a brief review of literatures.

A Case of Large Cervical Intradural Lipoma with Externsion into the Posterior Fossa

Intraspinal lipomas are rare, benign neoplasms, comprising less than 1% of all intradural spinal tumors. Such tumors occur in the thoracic and cervical region, however, extension into the posterior fossa is most unusual. A case of large cervical intradural spinal liplma with extension into the posterior fossa in adult female is presented. Clinical feature was slowly progressing quadriparesis. Brain and cervical spine computed tomography confirmed the diagnosis and Magnetic resonance imaging was very useful for delineation of the anatomy of the lipoma as an aid in planning the operation. Operative therapy consisted of combined suboccipital craniectomy, spinal laminotomy and laminoplasty, subtotal tumor decompression.