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Trigeminal Neuralgia & Hemifacial Spasm (Part I)
Trigeminal neuralgia is a kind of neuropathic pain. The trigeminal nerve is the fifth cranial nerve and consists of two main components – motor and sensory. The sensory part of trigeminal nerve gives rise to three branches that transmit sensations in the upper (ophthalmic), middle (maxillary), and lower (mandibular) portions of the face.
Patients with trigeminal neuralgia often describe the pain as sudden and severe, more like an electric shock or a sharp cut in the cheek or jaw area. It can be very intense and agonising. Patients often thought it was toothache and consulted a dentist first; some of them even have teeth extracted. The condition may become so severe and disabling that even touching the face, speaking, or eating can trigger electric shock like severe pain. The pain may be so severe that patients cannot shave or burst into tears once they start to speak.
On the other hand, hemifacial spasm is caused by motor nerve dysfunction. It is characterized by uncontrolled and repeated muscle contraction on one side of the face. Initially, it is just an infrequent twitching around the eye. As it gets more severe, there will be involuntary blinking in one eye and twitching in angle of mouth.
Q2. How are trigeminal neuralgia and hemifacial spasm related?
While trigeminal neuralgia is primarily a pain symptom and hemifacial spasm a motor nerve problem, they share a similar underlying cause: compression of intracranial nerve by blood vessels.
In trigeminal neuralgia, the trigeminal nerve is compressed by blood vessels at its initial segment near the brain stem, the blood vessel hit the nerve like a hammer as it pulsates. As a result, the nerve sends false signals to the brain which was perceived as painful stimulations on the face.
Hemifacial spasm occurs when the facial nerve (seventh cranial nerve) is compressed by blood vessels near the brainstem. With each heartbeat, the blood vessels pulse like a hammer and hit the nerve, thereby sending false signals to the facial muscles. These false signals are interpreted as instructions from the brain to contract muscles, leading to involuntary spasms.
Q3. What is the common cause of trigeminal neuralgia? What are the risk factors?
It is commonly seen that when the blood vessel near the nerve has become more tortuous and atherosclerotic, it may exert pressure on it. As blood pressure rises with age, the nerve gets more compressed, triggering the onset of the condition. Some other causes are less common, but should not be overlooked, such as multiple sclerosis, brain tumour, cerebral aneurysm, and vascular malformation. They can also cause nerve compression and neuropathic pain. Along with consultations and physical examinations, doctors may arrange brain MRI to rule out these underlying abnormal conditions.
Q4. What is the common cause of Hemifacial Spasm? What are the risk factors?
The symptoms of hemifacial spasm tend to be more severe when one feels stressed, tired or emotionally disturbed. When one feels tired or stressed, blood pressure may rise. If blood vessels are already pressing against the nerve, the pressure becomes higher as blood pressure increases. And the symptom becomes more pronounced.
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