Arteriovenous Malformation and Hemifacial Spasm: A Rare Presentation.

Sir,

Arteriovenous malformation (AVM) is a non-inherited congenital vascular abnormality, with arterial and venous shunts. It is a tangle of blood vessels in the brain which bypasses blood from normal tissues causing venous ischemia locally. AVM detection rate is 1.21/100,000 person-years (95% confidence interval [CI] 1.02–1.42). [1] The usual presentation of AVMs includes headache, bleeding, and stroke. Its association with hemifacial spasm is very rare. To date, less than 50 cases of posterior fossa AVMs presenting as hemifacial spasm have been reported in the literature. [23]

A 45-year-old male presented with hemifacial spasms involving the right side for 5 years duration. The general examination was unremarkable except for the right hemifacial spasm. Nervous system examination revealed Normal cognition, normal language, and speech. Cranial nerve examination was unremarkable except for right hemifacial spasms. There was grade-I spasticity in the right upper and lower limbs. Power was 4/5 in all limbs. Deep tendon reflexes were brisk in both limbs. There was bilateral extensor plantar response. The rest of the nervous system examination was unremarkable.

Magnetic resonance imaging of the brain revealed multiple flow voids at the level of the brain stem extending into the spinal cord [As shown in Figure 1a and b].

Figure 1

(a) T1-weighted (T1W) images showing multiple flow voids at the level of medulla extending into the foramen magnum. (b) T2W images showing multiple flow voids at the level of pons and right side of the prepontine cistern

CT angiography revealed multiple arterial feeders from vertebral, basilar and superior cerebellar arteries with drainage into anterior pontomedullary, anterior pontomesencephalic, and petrosal veins [As shown in Figure 2].

Figure 2

CT angiography revealed a large arteriovenous malformation in the brainstem region extending into the spinal cord with multiple arterial feeders. Spetzler and Martin grade 6 (Inoperable)

The present case is unusual in the association of hemifacial spasms with Posterior fossa AVM. Posterior fossa AVMs are rare vascular malformations, representing 7–15% of all intracranial AVMs. [4] The mean age of presentation of intracranial AVMs is 32.8 ± 15.0 years. In posterior fossa AVMs, the mean age is 42 years. Brainstem AVMs present even earlier, with a mean age of 32 years. Men and women seem to be equally affected.

Posterior AVMs are usually present with Headaches (13%), Seizures (19%, Focal type in around 30% cases) and Bleeding (62%, 50% being ICHs). [5] Cranial nerve palsies, often affecting trigeminal nerve, and facial nerve, have been associated with lesions in the cerebellopontine angle and brain stem. [6] To date, less than 50 cases of posterior fossa AVMs presenting as hemifacial spasm have been reported in the literature.

Hemifacial spasm (HFS) is characterized by unilateral facial nerve dysfunction presenting as intermittent painless, involuntary and spasmodic contractions of muscles. Wilson [3] introduced the subject of hemifacial spasm as follows: “Facial spasm may be cryptogenic or symptomatic, non- or postparalytic, uni- or bilateral, partial or total, tonic, clonic, tonic-clonic, or fibrillary. Common though it is, both causation and pathogenesis are obscure, while pathological data are scanty and ambiguous.”

Two hypotheses [7] have been proposed to explain the characteristic signs—spasm and synkinesis—of hemifacial spasms. According to the first hypothesis, the development of crosstalk between individual nerve fibers of the facial nerve at the location of the vascular compression leads to aberrant neural transmission, causing the spasms in patients with HFS. While the other hypothesis claims that spasms are a result of hyperactivity of the facial motor nucleus, that is developed as a result of the vascular compression (or irritation) of the root of the facial nerve.

Digre et al.,[8] after reviewing the literature, reported on the etiology of HFS. The most common cause was Vascular abnormalities (either by an artery [loop, aneurysm, malformation, etc], a vein, or both.), Tumors, Bony abnormalities, Trauma, and Demyelinating diseases.

Differential diagnosis of HFS relies on clinical examination. “Babinski 2 sign or other Babinski sign or brow-lift sign” is an important sign in diagnosing HFS. It is the simultaneous contraction of Orbicularis oculi and Frontalis during ipsilateral eye closure causing the eyebrow to move in the upward direction. This cannot be produced voluntarily. The data demonstrated a high prevalence (86%), high specificity (100%), and high interrater reliability (92%). [9]

Treating the underlying cause is found to be a reliable treatment in HFS. Symptomatic management includes using Botulinum toxin injection, Carbamazepine, Gabapentin, Pregabalin. In our case, HFS was managed using Gabapentin as AVM was inoperable.

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Conflicts of interest

There are no conflicts of interest.