Effects of General Anesthesia on High-Frequency Oscillations in Somatosensory Evoked Potentials

To determine the characteristics of high-frequency oscillations (HFOs) of cortical somatosensory evoked potentials (SEPs), the effect of general anesthesia on HFOs and low-frequency primary cortical responses was studied. The authors recorded SEPs elicited by median nerve stimulation directly from human brains of seven patients who underwent implantation of subdural electrodes before surgical treatment of intractable epilepsy. Recordings were made before and during general anesthesia. Changes in the number of HFOs and amplitude ratios of HFOs/primary cortical responses were analyzed. Under general anesthesia, the number of HFO peaks and the amplitude ratios were significantly decreased. General anesthesia induced remarkably decreased HFO activities when compared to low-frequency SEPs, suggesting that each of those originated from different generators. Possible relations between gamma-amino-butyric acid (GABA)ergic inhibitory interneurons and HFOs are discussed.

[Clinical application of ibudilast for elder patients with chronic subdural hematoma]

Ibudilast, an antagonist of platelet-activating factor receptors, was administered to patients with chronic subdural hematoma (CSDH) to assess its effectiveness in preventing recurrence. The remaining volumes of subdural hematomas on brain computed tomography were measured approximately 1-2 months after using ibudilast. The hematomas were significantly smaller and there was no recurrence. Ibudilast administration may be useful in the prevention of recurrence of CSDH.

[Multiple cerebral aneurysms and a contralateral occluded internal carotid artery associated with persistent primitive trigeminal artery]

The frequency of angiographic demonstration of persistent primitive trigeminal artery (PTA) is 0.06 to 0.6%. It is well recognized that approximately 13.8 to 27.8% of patients with PTA also have intracranial aneurysms. However their association with the contralateral occluded internal carotid artery (IC) has not been reported. We reported such an extremely rare case of PTA associated with multiple cerebral aneurysms and a contralateral occluded IC. A 61-year-old female suffered from sudden onset of severe headache with nausea and vomiting. When she was admitted to our hospital, she complained only of headache with nausea. Computed tomography demonstrated a diffuse subarachnoid hemorrhage. Angiography showed a ruptured anterior communicating artery (Acom). Aneurysm and a left IC-PC large aneurysm with a broad neck. The angiogram also demonstrated a left PTA originating from the cavernous portion of the left internal carotid artery and ending at the midportion of the basilar artery and the contralateral occluded IC in the cervical portion. An operation was performed at day 3 using the left pterional approach, and the two aneurysms were successfuly clipped using the suction-decompression method. The patient was discharged with no neurological deficits.

[Spontaneous intracranial hypotension associated with trochlear nerve palsy and bilateral chronic subdural hematoma]

Spontaneous intracranial hypotension (SIH) is a rare disease which is associated with variety of symptoms and signs including cranial neuropathies. Though diplopia occurred reportedly in about one fourth of SIH cases, trochlear nerve palsy has been reported only one case in the literature. A 71-year-old previously healthy male developed postural headache and nausea. After 15 days, he began to have diplopia caused by right trochlear nerve palsy. He consulted our hospital 2 months later because only diplopia was not recovered. Magnetic resonance imaging (MRI) showed bilateral thin chronic subdural hematoma (CSDH), brain sagging and downward brain stem displacement, but not ischemic change in brain stem. We suspected SIH for right trochlear nerve palsy, and he had symptomatic therapy. Two months later, he had burr hole surgery because of disturbance of consciousness and right hemiparesis due to progressive bilateral-CSDH. To say nothing of disturbance of consciousness and right hemiparesis, his trochlear nerve palsy was completely recovered after surgery at once. Follow-up MRI showed brain sagging and downward brain stem displacement were recovered.

The effects of stimulus rates on high frequency oscillations of median nerve somatosensory-evoked potentials--direct recording study from the human cerebral cortex

OBJECTIVES

To study the effects of different stimulus rates on high-frequency oscillations (HFOs) of somatosensory-evoked potentials (SEPs), we recorded median nerve SEPs directly from the human cerebral cortex.

METHODS

SEPs were recorded from subdural electrodes in 5 patients with intractable epilepsy, under the conditions of low (3.3Hz) and high (12.3Hz) stimulus rates.

RESULTS

Increased stimulus rates to the median nerve from 3.3 to 12.3Hz showed a pronounced amplitude reduction of HFOs when compared with the primary N20-P20, area 3b, and P25, area 1, responses.

CONCLUSIONS

HFOs were more sensitive to a high stimulus rate than the primary cortical responses, suggesting that the post-synaptic intracortical activities may greatly contribute to the HFO generation.

Dynamic changes in area 1 somatosensory cortex during transient sensory deprivation: a preliminary study

To investigate the neural plasticity in the somatosensory cortex, changes in somatosensory evoked potentials (SSEPs) during finger ischemia were evaluated and compared with those affected by touch or movement interference. Somatosensory evoked potentials were recorded in the vicinity of the central sulcus in four patients with intractable epilepsy. During electrical stimulation to a selected finger, ischemic anesthesia was induced in another finger. Effects of tactile or movement interference were examined during electrical stimulation to the selected finger by applying tactile stimulation to or inducing voluntary movement of the other finger. Dynamic SSEPs were recorded during varying levels of sensory deprivation and different types of interference, and the dynamic nature of the SSEP changes within an individual was studied in detail. Somatosensory evoked potential changes appeared during finger ischemia and tended to persist during the postischemic stage, which is indicative of sensory plasticity and the maintenance of new conditioning. Amplitudes of the early and late cortical components increased when complete finger anesthesia was induced-a sign of the unmasking phenomenon. Amplitudes of early cortical SSEPs decreased when ischemic anesthesia was incomplete, similar to the findings when tactile or movement interference was applied. Surrounding inhibition, therefore, may become dominant before the unmasking phenomenon appears in early cortical SSEPs.

[A case of bitemporal epilepsy that was well controlled after unilateral lobectomy]

Here we report a case of bitemporal epilepsy that was well controlled after unilateral temporal lobectomy. The patient was a 31-year-old woman, who was born in an asphyxia state and had a history of a febrile convulsion. Complex partial seizure(CPS) preceded by abdominal aura appeared at the age of three. Despite anticonvulsant medication, the seizures gradually increased in frequency and sometimes developed into secondary generalized convulsions. Her scalp electroencephalogram(EEG) showed interictal spikes and seizure activities arising from the bilateral temporal lobes. No apparent lateralities in regard to the size or blood flow at the hippocampus were detected by MRI and SPECT studies. Intracranial EEG monitoring revealed that 80% of the clinical seizures originated from the left mesial temporal lobe, which was the non-dominant side for speech and memory functions as demonstrated by Wada test. Therefore, we performed a left temporal lobectomy that resulted in the complete disappearance of CPS. The present case exemplified the usefulness of intracranial EEG monitoring to clarify the dominant epileptic focus for surgery.

Paroxysmal kinesigenic choreoathetosis associated with frontotemporal arachnoid cyst--case report

A 17-year-old male presented with paroxysmal kinesigenic choreoathetosis (PKC) associated with frontotemporal arachnoid cyst. Xenon-133 single photon emission computed tomography detected a slight but equivocal decrease in regional cerebral blood flow in the vicinity of basal ganglia associated with the PKC episodes. PKC continued after surgical removal of the cyst but was well controlled by oral administration of carbamazepine. Whether the pathogenesis of symptomatic PKC was associated with the cortical lesion could not be determined in the present case.