Types of Hemispherotomy

Hemispherotomy is a complex neurosurgical procedure designed to treat severe, drug-resistant epilepsy by disconnecting one hemisphere of the brain from the other. This operation is typically reserved for children with catastrophic epilepsy that originates from one side of the brain, often due to conditions such as Rasmussen’s encephalitis, hemimegalencephaly, or post stroke syndromes.

Hemispherotomy is considered a life-altering solution for children suffering from catastrophic epilepsy caused by conditions such as Rasmussen’s encephalitis, hemimegalencephaly, Sturge Weber syndrome, or post stroke epilepsy. These neurological conditions often cause severe developmental delays, paralysis, and frequent, uncontrollable seizures. When medications and less invasive options fail, hemispherotomy can offer long-term seizure relief and a chance at a more functional, seizure-free life.

What Is Hemispherotomy?

Before delving into the different types, it’s essential to understand what a hemispherotomy involves. Unlike a hemispherectomy, which removes an entire hemisphere of the brain, a hemispherotomy is less invasive and focuses on disconnecting the affected hemisphere from the healthy one. This functional disconnection stops the spread of epileptic signals while preserving as much brain tissue and function as possible.

Different Types of Hemispherotomy

The main goal of all hemispherotomy procedures is the same: to eliminate seizure activity originating from one hemisphere. However, each patient’s anatomy, underlying condition, age, and seizure pattern can differ significantly. As a result, neurosurgeons have developed multiple surgical approaches to tailor treatment more precisely and reduce risks associated with brain surgery.

1. Lateral Hemispherotomy (Peri-insular Hemispherotomy) :- Lateral or peri insular hemispherotomy is one of the most commonly used techniques. It involves disconnecting the brain through a corridor around the insular cortex, an area deep within the lateral surface of the brain. The procedure accesses the brain via both the supra insular (above the insula) and infra-insular (below the insula) windows.

   This technique is favored for its precision and ability to preserve key structures. It is often used when the insular region itself is involved in the seizure activity or when a tailored disconnection is required. The peri-insular approach provides excellent access to the ventricular system and corpus callosum, which are critical disconnection points.

   Advantages :-

   • Precise disconnection pathway

   • Minimal removal of brain tissue

   • Adaptable for complex seizure foci

2. Vertical Parasagittal Hemispherotomy (VPH) :- The vertical parasagittal hemispherotomy is another widely used method. In this approach, the surgeon gains access through the midline of the brain, vertically along the parasagittal plane. It involves creating a small opening near the top of the skull and moving downward through the lateral ventricle to perform the disconnection.

   VPH is especially beneficial for patients with severe brain malformations or when the cortex is highly atrophied or malformed, such as in hemimegalencephaly. This method enables surgeons to bypass malformed cortical tissue and go straight to deeper structures like the corpus callosum and basal ganglia for disconnection.

   Advantages :-

   • Ideal for patients with gross brain malformations

   • Avoids cortical manipulation

   • Offers effective seizure control with less cortical disruption

3. Trans Sylvian Hemispherotomy :- This approach uses the natural Sylvian fissure (a deep groove in the lateral brain surface) to access the target areas. The trans Sylvian hemispherotomy involves splitting the fissure and navigating between arteries and veins to reach the insula and underlying white matter connections.

   The trans-Sylvian route is often selected for patients who require precise access to the insular and opercular regions. While technically challenging, it allows the surgeon to navigate around eloquent (functionally important) areas of the brain and is particularly useful when the epileptic zone involves the deep brain structures close to the fissure.

   Advantages :-

   • Minimally invasive in terms of brain retraction

   • Good access to deep brain structures

   • Useful in carefully localized epileptic foci

4. Functional Hemispherectomy :- Though technically not a “hemispherotomy,” the functional hemispherectomy is often considered in the same category. It combines both removal and disconnection of parts of the affected hemisphere, usually including the temporal lobe, frontal lobe, and parts of the parietal lobe, while preserving deeper brain structures. The objective remains functional disconnection rather than complete resection.

   This method may be used when there is significant cortical damage or atrophy that makes disconnection alone ineffective. Functional hemispherectomy may offer more extensive seizure relief in patients with multifocal epileptic zones.

   Advantages :-

   • Useful for patients with severely damaged or scarred cortex

   • Can be customized for different seizure origins

   • Offers long term seizure freedom for many patients

Choosing the Right Hemispherotomy Technique

Selecting the most appropriate hemispherotomy technique is a highly individualized decision. Neurosurgeons evaluate several factors, including :-

1. The patient’s age and overall health

2. Location and spread of seizure activity

3. Brain MRI findings (extent of malformation or damage)

4. Previous surgeries or treatments

5. Cognitive and motor function of the affected hemisphere

Advanced neuroimaging, electroencephalography (EEG), and multidisciplinary team evaluations help determine the most effective and safest surgical approach for each patient.

Recovery and Prognosis

Regardless of the hemispherotomy type used, post-surgical recovery typically includes a combination of physical therapy, occupational therapy, and ongoing neurologic monitoring. Most patients experience a reduction or complete cessation of seizures, especially when surgery is performed early in life.

It’s important to note that the disconnected hemisphere will result in some degree of motor and sensory deficit on the opposite side of the body. However, due to neuroplasticity, especially in children, many patients adapt remarkably well and regain a significant level of function over time.

Conclusion

Understanding the various types of hemispherotomy is crucial for making informed decisions about epilepsy surgery. Each technique be it lateral (peri-insular), vertical parasagittal, trans Sylvian, or functional hemispherectomy has specific indications, benefits, and technical nuances. While the idea of disconnecting part of the brain may seem daunting, hemispherotomy has changed countless lives by offering seizure freedom and an improved quality of life.