Imidazoline I(2) receptor density increases with the malignancy of human gliomas.

BACKGROUND: Current glioma grading schemes are limited by subjective histological criteria. Imidazoline I(2) receptors are principally expressed on glial cells. OBJECTIVE: To investigate the feasibility of using the measurement of imidazoline I(2) receptor expression to differentiate glial tumours from other types of brain tumours and for grading the different gliomas. METHODS: The specific binding of [(3)H]idazoxan to imidazoline I(2) receptors was measured in homogenates from human gliomas of different grades. RESULTS: The density of imidazoline I(2) receptors was significantly greater in the three types of malignant glial tumours than in postmortem control brain or non-glial tumours. The increase in density correlated with the malignancy grade of the gliomas. No significant differences in affinity values were observed. CONCLUSION: These results suggest that the density of imidazoline I(2) receptors may be a useful radioligand parameter for the differentiation of glial tumours from other types of brain tumours and for grading the different gliomas.

Increased density of I2-imidazoline receptors in human glioblastomas.

A glial location has been proposed for the non-adrenoceptor [3H]idazoxan binding site termed the I2-imidazoline receptor. The specific binding of [3H]idazoxan in the presence of (-)adrenaline was measured in membranes from excised human glioblastomas (n = 6), meningiomas (n = 6) and normal brains (n = 6). The pharmacological profile of the [3H]idazoxan binding in astrocytic tumours was similar to that in normal brain, compatible with the presence of I2-imidazoline receptors. There was a higher density of I2-imidazoline receptors in astrocytic tumours (Bmax = 266 +/- 18 fmol mg-1 protein; p < 0.001) than in normal brain (Bmax = 54 +/- 4 fmol mg-1 protein), with no differences in affinity values. Almost no [3H]idazoxan-specific binding was shown in meningiomas. The results suggest that I2-imidazoline receptors may be a selective marker for glial tumours in the evaluation of intracranial neoplasms.

[Spontaneous internal carotid artery dissection as a cause of unilateral lower cranial nerve palsies]. / Disección espontánea de la arteria carótida interna como causa de parálisis de pares craneales bulbares.

We present a 60-year-old man with a complete right IX-XII nerve palsy (Collet-Sicard syndrome) due to spontaneous right internal carotid artery (ICA) dissection. Magnetic resonance imaging (MRI) and MR angiography (MRA) showed signs of subadventitial dissection of the right ICA with a mural haematoma that expanded the circumference of the vessel at the level of the retrostyloid space, adjacent to the IX-XII nerves. No narrowing of the lumen or aneurysms was found. Clinical recovery was excellent after treatment with only antiplatelet drugs. Cervical internal carotid artery dissection should be included in the differential diagnosis of lower cranial nerve palsies. MRI and MRA are noninvasive, reliable methods for diagnosis and follow-up, especially in subadventitial dissections.

Arteriovenous fistulas in the neck: diagnosis with color Doppler sonography.

We report the use of color Doppler imaging in the diagnosis of four arteriovenous fistulas in the neck region: two had a traumatic origin and two were spontaneous. A perivascular color artifact was the most common initial finding on color images to indicate the underlying abnormality. In all four cases, a low-resistance flow with high systolic and diastolic velocities was observed in the feeding artery. Although angiography remains essential before therapeutic embolization, color Doppler sonography may be an important tool for screening and follow-up of cervical arteriovenous fistulas.