This 41-year-old female presents with left hemifacial droop and spasm. Try to give the following questions a shot.
Q1 – The differential diagnosis for causes of hemifacial spasm includes:
(b) AICA vascular compression
(c) Multiple sclerosis
(d) PICA compression
(e) All of the above
Q2 – Other accepted neurovascular compression syndromes include all of the following, except:
(a) Trigeminal neuralgia
(b) Glossopharyngeal neuralgia
(c) Nervus intermedius syndrome
(d) Tongue fasciculation syndrome
Q3 – Hemifacial spasm related to vascular compression most often is generated from which vessel?
(a) Anterior inferior cerebellar artery or basilar artery
(b) Posterior inferior cerebellar artery or basilar artery
(c) Super cerebellar artery or basilar artery
(d) Posterior cerebral artery or basilar artery
Now, have a look at the first four images without arrows, and see what observations you can make. Then look at the duplicate images with arrows for key findings.
A1 – (e) all of the above
A2 – (d) tongue fasciculation syndrome
A3 – (a) anterior inferior cerebellar artery or basilar artery
The most common and well-defined neurovascular compression syndrome is trigeminal neuralgia which classically related to contiguity of a tortuous and low-drooping superior cerebellar artery in proximity to the trigeminal entry zone. The mechanism is presumed to be the creation of a zone of focal demyelination by the adjacent pulsatile vessel. This results in a syndrome of lancinating pain conforming to a trigeminal distribution or its divisions especially V2 followed by V3.
The best imaging method for assessing trigeminal neuralgia vascular loop compression is the raw data thin sections from an MRA.
Trigeminal neuralgia, also called “tic douloureux”, in its most classic form causes extreme, sporadic and sudden burning or shock-like pain that lasts from seconds to two minutes per episode. The attacks can occur in succession, in volleys lasting as long as two hours. This is known as type 1, or “TN 1.” In the atypical form or type 2, also known as “TN 2,” the pain is constant, aching, burning and stabbing.
The most classic imaging finding has already been described but the vascular compression may wear away the protective coating around the nerve, the so-called myelin sheath. Trigeminal neuralgia-type symptoms may also be seen due to “wearing away” or destruction of the myelin coat around the 5th nerve in multiple sclerosis (MS).
Trigeminal neuralgia most often occurs in people over age 50 but can occur at any age. In MS it is more frequent in young adults. It is more common in women than men with the incidence being 12 per 100,000.
ProScan Pearls: The differential diagnosis in a case like this includes post-herpetic neuralgia (often overlooked), cluster headaches, and TMJ disorder.
Besides looking for vascular compression, one of the most important aspects of MRI is excluding MS.
Isolated involvement in the third division of the trigeminal nerve is most uncommon.
Hemifacial spasm is the next most common vascular compression syndrome after tic douloureux and related to anterior inferior cerebellar artery or ectatic basilar compression of the seventh nerve complex at its entry zone.
Glossopharyngeal neuralgia features lancinating pain in the back of the throat and may be related to PICA or vertebral compression on cranial nerve IX.
Nervus intermedius syndrome (the sensory division of seven) results from seventh and eighth-nerve complex compression and presents as severe otalgias especially in the external auditory canal.
Tongue fasciculations are a diagnostic feature of ALS but have no vascular compression syndrome correlate involving nerve XII.
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1. R. Tesh. Hemifacial spasm. AJNR, Vol 12, issues 839-842.