|Lateral view showing mid portion basilar stenosis|
|Towns view showing severe mid basilar stenosis|
|Left intracranial vertebral stenosis near formation of basilar|
|Cervical vertebral stenosis at its origin|
Syn : Vertebra basilar insufficiency can result from either stenosis or complete occlusion of Vertebral and or basilar.
The posterior circulation consists of the vertebral arteries, the basilar artery, the posterior cerebral arteries and their branches. These arteries, through short penetrating branches and circumferential branches, supply the brainstem (medulla, pons, and midbrain), the thalamus, the hippocampus, the cerebellum, and medial portion of temporal and occipital lobes.
The vertebral arteries originate from the subclavian arteries and course through the vertebral foramina of C6-C2, around the atlas, and through the foramen magnum. At the pontomedullary junction both vertebral arteries join to create the basilar artery. The vertebral arteries supply the medulla, the pons and the cerebellum. The distal vertebral arteries and the basilar artery give rise to superior, anterior, posterior, and inferior cerebellar arteries that supply the cerebellum.
The vertebral arteries are prone to stenosis at their origin and at the junction with the basilar artery.
The basilar artery and its branches supply the pons and the cerebellum. Distally the basilar divides into the posterior cerebral arteries.
Stenosis can occur anywhere along the trunk of the basilar.
The posterior cerebral artery (PCA) supplies portions of the midbrain, the thalamus, medial temporal and occipital lobes.
Patients may present with a wide variety of syndromes.
Neurological dysfunction includes hemi or quadriparesis, cranial nerve deficits (III-XII), respiratory difficulty, altered sensorium, vertigo and ataxia. Multiple cranial nerve signs indicate involvement of more than one brainstem level.
Patients may present with only hemiparesis, which may progress rapidly to quadriparesis or a locked-in syndrome. The onset of symptoms may not be as abrupt as with anterior circulation strokes.
As the posterior circulation supplies the brainstem, cerebellum, and occipital cortex, the symptoms frequently involve the "5Ds": dizziness, diplopia, dysarthria, dysphagia, and dystaxia.
The hallmark of posterior circulation stroke is “crossed findings,” with cranial findings on the side of the lesion and motor or sensory findings on the opposite side.
The exact symptom complex depends on the precise location of the infarct.