Hemispherectomy is a technique in which the entire cerebral hemisphere is removed along with the white matter below and part of the basal ganglia after a large bone flap craniotomy, leaving only the thalamus and brain tissue below the hypothalamus.
History
The concept of hemispherectomy was first mentioned in 1886, but it was not until 1926 that Dandy performed the first true hemispherectomy in human history, removing all the anatomical structures of the cerebellar curtain on one side of the cranial cavity in order to treat a patient with an extensive infiltrating glioma in the right hemisphere. To distinguish it from later modifications, it was called an anatomic hemispherectomy, and was intended to be a radical treatment for patients with highly malignant gliomas. Since then, this procedure has been used clinically and some basic studies have been conducted. The recent results have been satisfactory, with many patients having better than expected results in terms of mental, personality, and casual movement of the contralateral limb after surgery. However, the long-term results were not satisfactory, and the survival rate was low due to postoperative infection, bleeding, and early tumor recurrence. This period is called the tumor stage of cerebral hemispherectomy. Zhang Kai, Department of Functional Neurosurgery, Tiantan Hospital, Beijing, China
In 1945, Krynauw applied this procedure to treat infantile spastic hemiplegia with intractable epilepsy. 12 cases were treated by 1949, and the patients’ symptoms improved significantly after surgery. The treatment of epilepsy was satisfactory without affecting muscle strength and cognitive function. Since then, this procedure has really developed, moving from the tumor to the functional phase. The number of hemispherectomies reported before 1956 was 75, of which no more than 20 were used to treat infantile spastic hemiplegia with intractable epilepsy, but by 1968 the number of reports of this procedure for infantile spastic hemiplegia with intractable epilepsy had increased to 420 worldwide.
However, as the postoperative recovery period continued to lengthen, it was found that one-third to one-quarter of these patients gradually developed neurological deficits, obstructive hydrocephalus, and mental retardation, with a mortality rate as high as 50%. The main reason for this is that the formation of a huge postoperative cavity causes the loss of support for the healthy cerebral hemisphere and the surgical stump, especially when the structure is mechanically oscillated by strenuous activities or some minor traumatic factors, as a result of which small amounts of exudation or bleeding occur from time to time in the originally mechanized subdural membrane, which is prone to bleeding, and enters the cerebrospinal fluid circulation through the interventricular foramen. After phagocytosis, the hemoglobin is deposited on the corresponding meninges, resulting in iron-containing heme deposits on the brain surface, leading to neuronal degeneration and gliosis, and causing various clinical symptoms.
The high mortality and incidence of this comorbidity has forced neurosurgical centers worldwide to reduce the clinical use of this procedure since 1970. However, the exceptional results of this procedure in the treatment of infantile spastic hemiplegia with intractable epilepsy remained in the minds of experts, especially after further understanding of the mechanisms of long-term comorbidities, and various modifications were introduced with the aim of reducing the mortality and incidence of long-term comorbidities, while maintaining the results of hemispherectomy. The modifications are divided into three main categories, namely functional hemispherectomy, cortical hemispherectomy, and anatomical hemispherectomy. Theoretically, it is better than the previous methods in terms of antiepilepsy and prevention of long-term complications.
Surgery
Functional hemispherectomy: In 1974, Rasmussen of the Montreal Neuroscience Institute (MNI) in Canada first proposed a hemispherectomy in which the central region and temporal lobe of the affected side were mainly removed, and the hemispherectomy was anatomically subtotal and functionally total. The hemisphere was first excised from the temporal lobe and then from the frontoparietal tissue behind the level of the pterygoid crest, including the posterior triangle and the paramedian structures. The frontal and occipital lobes are isolated. After resection, the EEG is checked and the insula is resected if there is a seizure focal point of insular origin. However, the antiepileptic effect is not satisfactory. Villemure reported 34 cases with an average follow-up of 8 years, 78% of which achieved significant results. In China, Nanjing General Hospital reported a satisfactory antiepileptic effect, and 7 of the 8 patients they followed up had complete disappearance of seizures.
Since epileptic discharges originate from neurons in the cerebral cortex, only the affected cerebral hemispheric cortex should be removed, and the white matter and basal ganglia outside the ventricular canal of the affected ventricle should be preserved. This can control epilepsy and ensure that the ventricular system does not communicate with the operative cavity. The antiepileptic effect is still unsatisfactory, with an efficacy rate of 70% to 80%, for the same reason as functional hemispherectomy, with some cortical remnants. He followed up 20 postoperative patients operated by this method, and 12 patients had complete cessation of seizures. At the same time, the operation is complicated and there is more intraoperative bleeding.
3. Anatomical modification: Chen Binghuan and Yang Jiongda of Beijing Tiantan Hospital proposed to block the muscle flap in the foramen monro and fix it on the cerebral falx and cerebellar curtain with a silk thread to prevent the muscle flap from falling off. At the same time, the convex dura was sutured proximally to the falx cerebri and distally to the basal ganglia, and sutured along the perimeter of the basal ganglia to the base of the middle cranial fossa and the cerebellar curtain at the lower end of the falx cerebri. Theoretically, this method is more reasonable than the above-mentioned methods in terms of antiepilepsy and prevention of long-term complications. Yang Jiongda reported 43 postoperative patients with complete control of epilepsy in 39 cases (91%) and basic control in 4 cases (9%), with no long-term complications.
Efficacy
The antiepileptic effect of hemispherectomy is very positive, with an efficiency rate of 90-96% and 67-77% of seizures disappearing. The data provided by the top Hopkins Hospital in the United States, for example, show that of the 58 hemispherectomies performed during a certain period of time, there were four deaths and three unsatisfactory outcomes, while 44 surgical results were very satisfactory and seven were more satisfactory.
In 1945, Krynauw began using this procedure to treat infantile spastic hemiplegia with epilepsy. 12 cases were performed over a four-year period until 1949, and except for one case of death from hemorrhagic shock, all seizures were controlled, abnormal behavior improved, and hemiplegia did not worsen or even improved, a result that even the operator did not expect. After decades of development, physicians around the world have been trying to improve this procedure for different postoperative complications, and good progress has been made, but some complications still exist, such as obstructive hydrocephalus and cerebral edema in the countermeasure hemisphere.
Regarding the recovery and reconstruction of neurological functions after hemispherectomy.
1, reconstruction of sensory and motor functions: Early extensive unilateral brain damage in children with residual significant sensory and motor functions, after hemispherectomy, the motor impairment on the hemiplegic side does not worsen after surgery, or the phenomenon of faster recovery of preoperative muscle strength and relief of spasticity after surgery is a strong reflection of the reconstruction of immature brain functions.
2. Recovery of language function: Previous studies have shown that the removal of the left hemisphere usually does not cause language deficits, and the right hemisphere can compensate for language function, as long as the child has the disease before the age of 5 years. Further studies have attempted to explain this phenomenon and why some right-hemisphere resected patients do not develop language well, while some left-hemisphere resected patients develop good language function. The plasticity of the right hemisphere in language development and higher recitation, at least in expressive language, is important; individual differences in brain maturation are significant and are related to the speed of language recovery after hemispherectomy.
3. Visual, auditory and other: Hemispherectomy does not have important effects on visual and auditory functions. Patients’ personality became milder and their deviant behavior improved after surgery, with an efficiency of more than 90%. Postoperative intelligence improved due to control of epileptic pain and discontinuation of antiepileptic drugs that had serious cognitive effects.
Indications
1. Intractable epilepsy: In patients with extensive cerebral hemisphere lesions with intractable epilepsy, with lesions limited to one hemisphere, epileptic discharges on the diseased side, and contralateral hemiparesis, hemispherectomy on the diseased side can be considered. For example, in 36 patients who underwent hemispherectomy in three years at Tiantan Hospital, seizures disappeared in 34 cases (94.4%) and decreased by more than 75% in 2 other cases. All 36 patients showed varying degrees of improvement in neuropsychological evaluation and IQ. Those who had aggressive behavior and frequent crying and screaming became quiet and adapted to their environment. It was previously thought that this procedure should be considered only for patients with an IQ of 60 or higher, but after surgery for patients with an IQ of less than 60, it was found that the IQ of the patients also improved.
2. Rasmussen syndrome: It refers to focal seizures known as a result of chronic focal encephalitis. The disease is most common in children and adolescents, especially in children before the age of 10 years. Seizures are manifested as focal limb convulsions, often starting from one limb, and are continuous. The seizures are divided into several stages, ranging from fewer seizures to a progressive increase in the number of seizures to progressive hemiparesis, hemianopia, aphasia, and cognitive impairment. These seizures are difficult to control with medications, so many patients have the option of surgical treatment. Although cerebral hemispherectomy may worsen the hemiparesis compared to the preoperative period, it is effective in relieving the convulsions and can enable the child to live a normal life. For children with cerebral hypoplasia, early surgery can also lead to normal development.
3. Hemiplegia-paralysis-epilepsy (HHE) syndrome: It is a sequelae caused by convulsive seizures, mostly occurring in children and young adults, with a history of convulsive fever as a child or secondary hyperthermia due to dysentery and pneumonia. The first thing that occurs is hemiparesis, followed by epileptic symptoms.
It is important to note that for hemispherectomy, the younger the age of surgery, the more pronounced the results, and the better the clinical recovery. If the left hemisphere is removed, language skills will be affected, but some studies have shown that removal of the left hemisphere usually does not cause language deficits, and the right hemisphere can compensate for language function, as long as the child has the disease before age 5. In the case of vision and hearing, hemispherectomy does not have a significant effect.
In addition, hemispherectomy does not have serious effects on personality and memory, and the younger the patient is, the better the recovery, but it does result in a loss of physical function on the other side of the hemisphere. Therefore, hemispherectomy is a surgical treatment to be considered for patients who have already developed motor impairment on one side of the body and wish to remove the pain associated with seizures.