Rare Complication of Microvascular Decompression: Delayed Facial Paralysis

A 44-year-old woman with a history of hypertension and a chief complaint of left-sided facial pain in the V2 and V3 distributions, which had been ongoing for 4 months. MRI of the brain with trigeminal protocol revealed that the left Superior Cerebellar Artery (SCA) was in close contact with the cisternal segment of the left trigeminal nerve near its root entry zone, indicating a potential cause for trigeminal neuralgia. She underwent Microvascular Decompression (MVD) surgery, a common procedure used to relieve trigeminal neuralgia by separating the offending vascular structures from the trigeminal nerve, which led to resolution of her facial pain. However, during follow-up, the patient developed grade 1 facial paralysis, which suggests a complication related to the surgical intervention. (Figure 1 & 2)

Patient presenting with grade 1 facial paresis and mild imbalance while walking. (Figure3)

Facial paralysis following microvascular decompression can occur due to a few possible reasons:
1. Direct Injury to the Facial Nerve: The facial nerve (cranial nerve VII) runs in close proximity to the trigeminal nerve in the brainstem and may be inadvertently injured during the surgical procedure, especially if the decompression requires manipulation of surrounding structures.
2. Trauma from Retraction: In some cases, retraction of the cerebellum or the brainstem during surgery may cause mechanical injury to the facial nerve.
3. Post-operative Edema or Compression: After MVD, post-operative swelling or hematoma can put pressure on the facial nerve, leading to temporary or permanent paralysis.
4. Ischemia or Vascular Compromise: There is also a risk of ischemia to the facial nerve if blood flow is disrupted during the surgery, although this is less common.
5. Pre-existing Subclinical Facial Nerve Dysfunction: In some cases, a prior undiagnosed issue with the facial nerve (such as minor compression or preexisting vulnerability) may become symptomatic postoperatively. Repeat MRI done shows pseudomenigocele and inflammatory changes around facial nerve. Patient was started on high dose steroid there was gradual improvement in the facial weakness and gait. Pure tone audiometry showed bilateral minimal hearing loss. No retraction injury to auditory nerve. (Figure 4 & 5),

It is crucial to thoroughly evaluate and monitor post-surgical conditions. Delayed facial weakness may be attributed to gradual edema occurring after surgery. The use of Teflon to separate nerve tissue and blood vessels, although beneficial, can sometimes be perceived as a foreign body leading to inflammation. [1-4] Facial weakness can be managed with facial muscle exercises without requiring special treatment. [5-7] Several treatments have been proposed to address DFP including steroids, acyclovir, and facial canal decompression. But in most cases spontaneous resolution occurs, and the average duration of improvement is 5.7-9 weeks. [8,9]

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