fMRI changes in the brain associated with the carotid compression test

PURPOSE

The purpose of our investigation was to study in normal volunteers the response to a unilateral common carotid (CC) compression test using dynamic MRI sensitive to variations in blood magnetic susceptibility.

METHOD

Nine volunteers, positioned in a 1.5 T MR scanner, performed a unilateral 40 to 45 s CC self-compression during the acquisition of single slice axial T2*-weighted FLASH images.

RESULTS

In three subjects, the signal showed a significant 2% drop from baseline in the ipsilateral frontal temporal cortex during the compression. In another three subjects, a significant 1.5-2% signal decrease was observed in both hemispheres. In two subjects whose MR angiography showed abnormalities of the circle of Willis, the bilateral signal drop was more remarkable (3%). In one volunteer, the signal did not change.

CONCLUSION

Increased deoxyhemoglobin within the brain microcirculation is the probable explanation for the signal drop. This method could be further tested in view of the widespread use of open interventional MR units.

[The use of TCD in intensive care and for identification of complications in subarachnoid hemorrhage ]

Transcranial Doppler (TCD) is at present the only exam to allow non-invasive, bedside monitoring of cerebral vasospasm after SAH. The high temporal resolution of this technique enables detection of fast flow-velocity changes occurring in intracranial arteries, as well as evaluation of vasomotive reserve and strength of autoregulation. TCD results concerning cerebral vasospasm evaluation are comparable to those obtained in angiographic studies; however the correlation between TCD data and clinical status is not always so strict. This difference could be explained by the fact that TCD measures flow velocity and not flow in intracranial vessels.

Differences between the concentrations of antiepileptic drugs in normal and pathological human brain

The concentrations of antiepileptic drugs in histologically normal and pathological brain tissues were investigated in 6 patients submitted to surgery. No significant difference for phenobarbital and phenytoin was found between normal and scar tissue, whereas there was a trend to concentration in tumour tissue (meningioma and glioma) of phenobarbital, phenytoin and carbamazepine. Alteration in the vascular supply and pathological changes at cellular and subcellular levels could be responsible for the differences in the distribution of the drugs. The possible clinical relevance of the preferential concentration of the drugs in tumour tissue is discussed.

Late results of stereotactic radiofrequency lesions in epilepsy

Thirty-five patients with partial complex seizures and two patients with generalized epilepsy were treated by stereotactic radiofrequency lesions. Follow-up from 2 to 13 years was available in 30 patients. The stereotactic targets in patients with partial complex seizures were: a) Amygdala; b) Ammon's horns; c) parahippocampal gyrus; d) Fornix. Depending on scalp EEG and depth electrode studies, each patient had one or more target coagulated, unilaterally or bilaterally. In the 2 cases of generalized epilepsy, bilateral Forel field lesions were performed. Late surgical results are discussed in relation to the depth EEG studies and the number and site of stereotactic lesions.

Stereo-EEG and surgery in partial epilepsy with temporo-parieto-occipital foci

Six cases of partial epilepsy operated on for lesions at the temporo-parieto-occipital junction are presented. Three cases had signs of enlargement of one lateral ventricle at the temporo-parieto-occipital carrefour, three had a lateral homonymous hemianopsia and all showed lateralizing interictal EEG abnormalities. The manifold features of the seizures could not be related to the involvement of one or more definite cortical areas. Since clinical, radiological, scalp EEG investigations provided no sufficient data to map the epileptogenic lesion to be excised, stereo-EEG studies with chronic depth electrodes were performed. Besides permitting the exact delimitation of the epileptogenic lesion, depth EEG gave the clue for interpreting physiopathological mechanisms underlying the electroclinical seizures in each case.

Indications of anticonvulsant plasma levels monitoring in medical and surgical treatment of epilepsy

The results of long-term (19-21 months) intensive anticonvulsant plasma levels monitoring in two patients with partial complex epilepsy resistant to therapy are reported. In the first case the qualitative and quantitative therapeutic adjustment based on the monitoring data caused the disappearance of the seizures. In the second case, in which a right mid-temporal calcification (abscess) was demonstrated by CT-scan, the attacks were not controlled by different drugs. The patient became seizure-free after a right temporal lobectomy. The importance of long-term anticonvulsant plasma levels monitoring in partial complex epilepsies unresponsive to pharmacological therapy is discussed in detail in view of possible surgical treatment.

[Experimental model of vascular microanastomosis applicable in neurosurgery]

A model for vascular microanastomosis is presented. Attention is drawn to problems involved in the technique for such operations and it is shown that results can be greatly improved by using a microscope. Six-month angiographic follow-up results in a personal series are illustrated and some clinical indications for this form of surgery are explained.