When considering surgery as a treatment option, it is important to consider all the benefits and risks. Decisions about proceeding with a more invasive treatment must always be highly individualized. For infants and young children with only gelastic seizures, the decision to “watch and wait” may be the most comfortable decision for some families. However, it is important to understand that studies have found that 50% of children with only gelastic seizures in the early years will develop the deteriorating form of the HH syndrome (loss of developmental milestones and progressive impairment of learning and cognition) and that up to 75% to 100% will develop other seizure types in their lifetime. Further research needs to be done comparing the outcomes of individuals who choose to intervene early versus those who delay.
All surgical approaches should be preceded by a detailed preoperative evaluation. The evaluation normally includes assessment of cognitive deficits, behavior disturbances, seizure severity, and the HH classification or type.
Several successful surgical approaches are now being used which allow for complete removal or partial resection and disconnection of an HH. With the advances in surgical techniques and experience, many HH treatment centers are recommending early intervention based on quality of life comparisons. For a list of questions to ask your surgeon if you are contemplating HH surgery, click here.
These surgical approaches include: a) Transcallosal anterior interforniceal approach (TAIF); b) Endoscopic resection/disconnection; and c) Orbitozygomatic approach. In some cases, surgeons have elected to do a combination of these approaches. The choice of the surgical approach is based upon the anatomy of the HH lesion of each patient.
Transcallosal Anterior Interforniceal Approach
Surgical options for HH patients took a giant step forward in 2001, when Dr. Jeffrey Rosenfeld of Melbourne, Australia, developed a new surgical approach to the hypothalamic hamartoma. His approach is known as the Transcallosal Anterior Interforniceal Approach. It is often the approach of choice for a larger HH. Most HHs are attached to one or both sides of the hypothalamus and protrude into the third ventricle, making them accessible for resection or disconnection via this approach. The main advantage of this approach is the excellent surgical view provided. A second advantage is the ability to resect (remove) and/or disconnect the HH and minimize injury to the mammillary bodies and other critically important structures that reside underneath or adjacent to the HH tumor. By approaching from above, there is less risk to the major blood vessels and cranial nerves at the base of the brain.
Seizure reduction after surgery has been very promising with this approach. In addition to a reduction in seizure frequency after resection, significant improvements in behavior, reduced aggression, increased concentration, and improved mood have been reported.
Complications have been reported with the transcallosal approach. In a few cases, when attempting a complete removal of the HH, injury to the hypothalamus has occurred. One of the more common complications is diabetes insipidus (DI). With DI, the kidneys are unable to conserve water and symptoms include excessive thirst and excessive urine output. DI can be successfully treated by a nasal spray (desmopressin, also known as DDAVP) administered one or more times a day. In most cases this condition resolves itself, while in some it has to be treated long term.
Another common complication after surgery is difficulty with short-term memory. The published research studies have reported that short-term memory issues are common. These resolve over time (usually days or weeks post-surgery) in most patients, but short-term memory impairment may be permanent in 10% of patients. (It is important to be aware that most HH patients have short-term memory problems even prior to surgery.)
A commonly encountered problem (10-20%) is increased appetite and weight gain. Rare problems include sleep disturbance, temperature instability, or panhypopituitarism (a deficiency in several pituitary hormones, including thyroid and growth hormone) for which replacement therapy is required.
Transventricular Endoscopic Resection/Disconnection
Transventricular Endoscopic Resection or disconnection has proven to be a good treatment option for smaller HHs ideally attached to only one wall of the third ventricle. In some cases, the HH is easily distinguished from the surrounding hypothalamus as a mass projecting into the third ventricle and light brown in color. The center of the HH is removed and where possible, the interface with the hypothalamus is carefully separated. Some surgeons believe that completely disconnecting the HH from the surrounding tissue is equally as effective as surgery with complete resection or removal of the HH tissue.
Seizure freedom outcome has been similar to the transcallosal approach and significant improvement in behavior has also been reported. Compared to the transcallosal approach, endoscopic resection usually results in a shorter hospital stay. Surgical complications are similar to the transcallosal approach.
Until the relatively recent introduction of the Transcallosal and Endoscopic approaches, resective surgery for HH was most often performed with a surgical approach from below. This approach is known as the orbitozygomatic or pterional approach. Today, with the introduction of the pathway from above, the orbitozygomatic approach is usually restricted to pedunculated HH lesions that hang down below the floor of the third ventricle. The advantage of approaching pedunculated HH lesions from below includes a shorter distance to the HH. Pedunculated HHs typically have a narrow base of attachment, and the approach from below allows the surgeon a direct view of the lesion. For large lesions that have a base in the third ventricle but may also have a component that hangs down below the third ventricle, a combination of approaches may be required for complete resection.