Microvascular Decompression Surgery for Hemifacial Spasm: A Step-by-Step Guide
Understanding Hemifacial Spasm and Its Surgical Treatment
Hemifacial spasm is a relatively common neurological condition treated within neurosurgery. It is characterized by involuntary twitching or muscle contractions, typically starting around the lower eyelid and progressively spreading to other areas of one side of the face. These spasms are often caused by vascular compression of the facial nerve at its root exit zone from the brainstem. While medications and Botox injections may offer temporary relief, microvascular decompression (MVD) remains the most effective long-term solution for patients seeking permanent symptom resolution.
The Surgical Approach: Accessing the Cranial Nerves
Initial Incision and Craniotomy
The MVD procedure begins with a small incision—approximately 5 centimeters—made behind the ear on the affected side. This postauricular approach allows surgeons to access the posterior cranial fossa with minimal disruption to surrounding tissues. After carefully dissecting through the layers of muscle and connective tissue, the surgeon exposes a small section of the skull. Using a high-speed surgical drill, a precise opening about 1.5 cm in diameter is created—a process known as a craniotomy. This critical step provides safe entry to the intracranial space without damaging underlying brain structures.
Dura Opening and Microscopic Visualization
Once the bone flap is removed, the dura mater—the tough outer membrane covering the brain—is incised in a "T"-shaped pattern using a sharp scalpel. The dural flaps are gently retracted and secured to allow optimal exposure. At this stage, the operating microscope is introduced to provide magnified, high-definition visualization of the surgical field. This level of precision is essential when navigating delicate neural and vascular anatomy deep within the brain.
Intracranial Exploration and Neurovascular Assessment
Retracting the Cerebellum and Identifying Key Structures
With microscopic guidance, the cerebellum is gently mobilized to create a narrow corridor to the brainstem. Surgeons carefully navigate between natural anatomical planes to minimize trauma. The goal is to visualize the seventh (facial) and eighth (vestibulocochlear) cranial nerves as they emerge from the brainstem. Special attention is given to the root entry zone of the facial nerve, which is commonly compressed by an adjacent blood vessel—often the anterior inferior cerebellar artery (AICA) or a branch of the superior cerebellar artery (SCA).
Identifying the offending vessel is crucial to the success of the operation. In some cases, venous compression may also be present, requiring careful evaluation and management. Advanced imaging such as MRI with FIESTA or CISS sequences prior to surgery helps anticipate vascular anatomy, but intraoperative findings ultimately guide the surgical strategy.
Decompression and Long-Term Fixation
Once the compressing artery is identified, it is carefully dissected away from the facial nerve. To prevent recurrence, a soft, biocompatible material—commonly a sterile Teflon felt or synthetic sponge-like polymer—is inserted between the vessel and the nerve. This padding acts as a cushion, shielding the nerve from pulsatile contact while preserving blood flow in the vessel. The placement is meticulously adjusted to ensure complete decompression without introducing new tension or injury.
Closure and Recovery
After confirming adequate decompression and hemostasis, the dura is closed watertight using sutures and sometimes reinforced with a dural substitute or sealant. The bone flap is typically left out or replaced depending on institutional protocols, and the muscular and subcutaneous layers are sutured in succession. The skin is then closed with staples or sutures, completing the procedure.
Patients usually remain in the hospital for 2–4 days postoperatively for monitoring. Most report significant improvement or complete resolution of facial twitching within weeks. As with any major neurosurgical intervention, potential risks include hearing changes, facial weakness, cerebrospinal fluid leak, or infection—though complication rates are generally low in experienced centers.
Microvascular decompression offers a definitive cure for many patients suffering from hemifacial spasm, restoring both function and quality of life. With proper patient selection and expert surgical technique, MVD continues to be the gold standard treatment for this often-disabling condition.