Hemifacial spasm is an analogous disease to trigeminal neuralgia. Instead of a small brain blood vessel compressing the trigeminal nerve, an artery compresses the facial nerve as it exits the brainstem and this causes hemifacial spasm. This condition is approximately ten times less common as trigeminal neuralgia affecting somewhere between 0.8 and 10 people /100,000. Hemifacial spasm usually appears as twitching or spasms of the orbicularis oculi muscles that close the eye. It will then typically spread to the lower face. More rarely it may begin in the orbicularis oris muscles at the corner of the mouth. It will then typically spread up the face to involve the orbicularis oculi. Rarely it may start in the upper and lower face at the same time. It would be very rare to occur bilaterally, and that would raise the question of the diagnosis being some other type of movement disorder. Over time, the spasms often become more frequent and last longer.
Like with trigeminal neuralgia, microvascular decompression surgery can be very effective in relieving the symptoms. In hemifacial spasm the immediate results of surgery are not quite as good as the excellent results expected in trigeminal nerve microvascular decompression surgery. Surgery is not immediately successful in all patients. This may be because an offending small vessel was not visibly appreciated at surgery, and sometimes early reexploration surgery within the first few days of the original operation in patients can be helpful. Other times, persistence of spasm can be due to resetting and hyperexcitability of the motor neurons in the facial nerve nucleus in the brainstem resulting from prolonged short-circuiting by cross-talk between the nerve fibers at the point of neurovascular compression. The probability of being completely spasm free immediately after surgery is approximately 60%. However, by 6 months after surgery the spasms will be gone in approximately 90% of patients.
Unlike trigeminal neuralgia, medication is not typically effective in hemifacial spasm. Temporary improvement can be obtained with Botox injections. However, this is associated with some muscle weakness, and the benefits will only last 3 months before reinjection of Botox is necessary. Botox will not cure this disorder. Surgery is the only treatment that offers the possibility of a cure for this disorder.
The video shows a patient undergoing microvascular surgery for hemifacial spasm on the left side. An opening in the skull slightly smaller than a nickel is made. This is the magnified view seen by the neurosurgeon through the operating microscope. The large linear white structure to the right of the surgical instrument is the cochlear nerve (the auditory nerve). The facial nerve is seen just beneath and to the left of the cochlear nerve when the surgical instrument gently retracts the nerve. A loop of artery can be seen, which is moved away from the facial nerve as it exits the brainstem, and a piece of Teflon felt is gently placed between the nerve and the artery. This Teflon will remain in place and some fine scar tissue will ultimately stabilize it so that it does not move.