Amygdalohippocampectomy is a surgical procedure that removes the amygdala and hippocampus, which are parts of the brain found in the temporal lobe that forms part of the limbic system.
Both the hippocampus and amygdala play a significant role in body control and memory. As such, the surgery itself is risky and considered only when other methods of treatment fail to address epilepsy. One of the possible serious complications is memory dysfunction.
In general, a hippocampus removal surgery is performed on patients who have been diagnosed with epilepsy. Epilepsy and seizures are usually used interchangeably or together. Although they are very similar, they are also different. Seizure describes the sudden increase of electrical or neural activity in the brain, and it is considered as just one event. Epilepsy, on the other hand, occurs if more than one seizure is happening in the brain. Simply put, a person can have a seizure without being diagnosed as epileptic, while epileptic individuals experience seizures.
There are many types of epilepsy, but amygdalohippocampectomy is recommended for patients whose seizures originate in the temporal lobe, specifically the medial structure. This can be verified by different imaging tests on the brain such as an MRI.
Seizures can differ greatly from one individual to another, and it is possible for a patient to have varied manifestations.
The outlook of the procedure as far as controlling the epilepsy is concerned is good. In one of the neurological studies on the different approaches for hippocampus resection, half of the patients reported not having seizures for at least five years, depending on the approach and how much of the mesial structure has been removed.
Neurosurgeons can implement different techniques to perform amygdalohippocampectomy and they can be generally classified as selective since only the affected tissues are removed, sparing the brain from as much damage as possible. Surgeons also used tools such as neuronavigation system for accuracy and guidance.
During surgery, the patient is administered with general anaesthesia with his vital signs monitored throughout the procedure. The head is tilted, and except for the part where the incision is made, the rest is covered with a surgical drape.
The periosteum and dura are accessed until the surgeon reaches the temporal gyrus. In the cortical approach, the incision for the entry point should not go beyond 3.5 cm from the temporal lobe. In the Transylvanian approach, the surgeon passes through the Sylvian fissure and an incision of 15 mm is made in the temporal stem. The uncus is removed first followed by the amygdala and the hippocampus.
After the procedure, all the incisions are closed, and the patient stays in the hospital for a few days for close monitoring and immediate follow-up.
One of the biggest risks of the hippocampus removal is the recurrence of seizures, which happens when some parts of the hippocampus and amygdala are not removed. This may mean the patient has to go through another round of surgery. Because of the delicateness of the procedure, some parts of the brain may be affected and become damaged. Depending on the procedure, the patient may develop vascular spasm, injury, brain hemorrhage, and infection. Some may experience problems with their vision or poor memory.
Wiebe S, Blume WT, Girvin JP, Eliasziw M,. A randomized, controlled trial of surgery for temporal-lobe epilepsy. N Engl J Med. 2001 Aug 2. 345(5):311-8.
Spencer DD, Spencer SS, Mattson RH, Williamson PD, Novelly RA.Access to the posterior medial temporal lobe structures in the surgical treatment of temporal lobe epilepsy. Neurosurgery. 1984 Nov. 15(5):667-71.[Medline]