Vertebrobasilar dolichoectasia and other arterial abnormalities leading to abducens nerve palsy.

INTRODUCTION: Dolichoectatic vessels can cause cranial nerve dysfunction by either direct compression or ischemia. Abducens nerve palsy due to neurovascular compression by elongated, enlarged, tortuous or dilated arteries is an uncommon but important cause. AIM: To highlight neurovascular compression as a cause of abducens nerve palsy and discuss various diagnostic techniques. METHODS: Manuscripts were identified using the National Institutes of Health PubMed literature search system. Search terms included abducens nerve palsy, neurovascular compression, dolichoectasia and arterial compression. Inclusion criteria required that the articles were written in English. RESULTS: The literature search identified 21 case reports where abducens nerve palsy was due to vascular compression. Out of these 18 patients were male and the mean age was 54 years. Eight patients had unilateral right abducens nerve involvement; eleven patients had unilateral left nerve involvement and two patients had bilateral involvement. The arteries causing the compression were basilar, vertebral and anterior inferior cerebellar arteries. A compressed abducens nerve is not usually clearly detected on CT (Computed Tomography) or MRI (Magnetic Resonance Imaging). MRA (Magnetic Resonance Angiography), Heavy T2- WI (weighted imaging), CISS (constructive interference in steady state) and FIESTA (Fast Imaging Employing Steady-state Acquisition) are essential to demonstrate vascular compression of the abducens nerve. The various treatment options included controlling hypertension, glasses with prisms, muscle resection and microvascular decompression.

Abnormalities of the Vertebrobasilar Arterial System Leading to Sleep Disorders.

INTRODUCTION: The abnormalities in the vertebrobasilar arterial system such as enlarged, tortuous or dilated arteries and aneurysms can generate pressure and distortion of brain structures especially in the medulla and pons. This brainstem compression by abnormal arteries can lead to various sleep disorders such as sleep related hypoventilation, central sleep apnea, obstructive sleep apnea, and positional sleep apnea. AIM: To highlight brainstem compression due to vascular abnormalities as a cause of sleep disordered breathing. METHODS: Manuscripts were identified using the National Institutes of Health PubMed literature search system. Search terms included sleep disorders, vertebrobasilar dolichoectasia, tortuous vertebral arteries, vertebrobasilar aneurysms, vascular compression and brainstem compression. Inclusion criteria required that the articles were written in English, highlighted both a sleep disorder and a vascular abnormality. RESULTS: The literature search resulted in 10 case reports where vascular abnormalities were leading to sleep disorders. Out of these: four patients had central sleep apnea; three had sleep related hypoventilation; one had positional central sleep apnea; one had positional central apnea along with obstructive sleep apnea; and one had obstructive sleep apnea. The various vascular lesions identified were: megadolichobasilar artery; dolichoectatic vertebral artery; fusiform vertebrobasilar aneurysm; tortuous and elongated vertebral arteries; calcified vertebral artery and medullary telangiectasia. CONCLUSIONS: Arterial compression of the respiratory centers in the pons and medulla can lead to central sleep apnea. Obstructive sleep apnea can also result from vascular compression of the medulla. The proposed mechanism is compression of nucleus ambiguus which controls pharyngeal tone. Pressure on cranial nerves IX and X can lead to pharyngeal dysfunction leading to occlusive apnea.