- Silent ischemic Brain damages
Microvascular Cranial Nerve Palsies
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Interruption of the blood supply to one of the cranial nerves causes it not to work. If there is interruption of signal to the VIth nerve (which innervates the lateral rectus muscle) the affected eye will not be able to move to the outside. If the IVth nerve is affected (innervating the superior oblique muscle) the eye will deviate upwards and inwards. Patients rapidly discover that they may be able to eliminate or decrease the double vision by tilting their head towards the opposite shoulder. When the IIIrd nerve (which goes to multiple muscles) is involved the eye may be limited in up, down, and gaze toward the nose. The eye can be deviated downwards and outwards. A 7th cranial nerve palsy creates an asymmetry in the smiles and bulk and tone of the cheek muscles.
In the case of microvascular interruption we are not sure what causes the loss of blood flow (which deprives the nerve of oxygen). This may occur due to blockage of small arteries related to high blood pressure, hardening of the arteries, or derailments of systemic or local blood pressure forces through the blood vessels and microcirculation.
An example of a 6th cranial nerve palsy in video animation is below. The palsy can be subtle to profound. Gaze transitions pick up the asymmetry in movement of the eyes in the horizontal plane of eye movements. This is ischemic brain damage until proven otherwise.
