Hemispherectomy

Last updated
Hemispherectomy
ICD-9-CM 01.52
MeSH D038421

Hemispherectomy is a surgery that is performed by a neurosurgeon where an unhealthy hemisphere of the brain is disconnected or removed. There are two types of hemispherectomy. Functionalhemispherectomy refers to when the diseased brain is simply disconnected so that it can no longer send signals to the rest of the brain and body. Anatomical hemispherectomy refers to when not only is there disconnection, but also the diseased brain is physically removed from the skull. This surgery is mostly used as a treatment for medically intractable epilepsy, which is the term used when anti-seizure medications are unable to control seizures.

Contents

History

The first anatomical hemispherectomy was performed and described in 1928 by Walter Dandy. This was done as an attempt to treat glioma, a brain tumor. [1] The first known anatomical hemispherectomy performed as a treatment for intractable epilepsy was in 1938 by Kenneth McKenzie, a Canadian neurosurgeon. [2] Krynaw, a neurosurgeon from South Africa, was one of the first to perform and report a case series on hemispherectomies in 1950. He performed the surgery on pediatric patients with infantile hemiplegia, specifically as a treatment for their seizures and cognitive impairment. [3] His hemispherectomy technique removed the damaged hemisphere except the thalamus and caudate structures. Krynaw reported good outcomes overall, although there was one post-operative death. Specifically, there was an overall theme of improvement in weakness, spasticity and cognition. [3] Amazingly, ten out of the twelve patients had seizures prior to the operation and none of the patients had seizures afterwards. [3] Other neurosurgeons began performing hemispherectomies as well, primarily for the treatment of seizures. For the most part, the surgeries would go well initially, but there was a general theme of subsequent deterioration and even death years after the surgery. As a result of the complication risk and the introduction of new anti-seizure medications, the popularity of the procedure began to decline in the 1950s. [4] Oppenheimer and Griffith were one of the first to describe the potential complications, and they reported their findings in 1966, describing superficial hemosiderosis, granular ependymitis and obstructive hydrocephalus. [5] They posited a theoretical solution to this problem, a surgery that is now known as a functional hemispherectomy. [5] Rasmussen was one of the first neurosurgeons to develop and apply a functional hemispherectomy in practice. He initially made modifications to the original hemispherectomy by preserving the least epileptogenic quarter or third of the hemisphere, hoping this would ameliorate the known complications of the original anatomic hemispherectomy. Although this modification seemed to solve this issue, patients undergoing the modified hemispherectomy continued to have seizures, which was problematic. Therefore, he further modified his surgery to functionally sever residual portions of the frontal and parieto-occipital lobes. [4] This surgery, the functional hemispherectomy, has been further modified over the years by several different neurosurgeons, and to this day there is not a consensus as to which exact technique should be used. Hemispherotomy refers to some of the more recently developed approaches to disconnect the epileptic hemisphere while minimizing brain removal and the risk for complications. [6]

Nomenclature

There are two main types of hemispherectomy: Anatomical and Functional.

Anatomical hemispherectomy refers to the resection and removal of an entire hemisphere of the brain, which includes all four lobes, with or without the removal of basal ganglia and thalamus. [6]

Functional hemispherectomy refers to surgeries that disable the function of one hemisphere, while maintaining its blood supply and without physically removing the entire hemisphere from the skull. [6] Functional hemispherectomies are performed more frequently than anatomical hemispherectomies due to their lower complication rates. [7] However, they do carry a risk of incomplete disconnection, which refers to when the surgeon inadvertently leaves remnants of fibers that continue to connect the hemisphere to the brain and body. These remaining fibers can be problematic, as they may lead to seizure recurrence.

Another term that falls under the hemispherectomy umbrella includes hemidecortication, which is the removal of the cortex from one half of the cerebrum, while attempting to preserve the ventricular system by maintaining the surrounding white matter. Hemidecortication was originally developed as a possible strategy to mitigate some of the complications seen with complete anatomical hemispherectomy. [6]

The term hemispherotomy refers to a surgery that is akin to a functional hemispherectomy in that it functionally severs the damaged hemisphere from the other and leaves some of the severed hemisphere within the skull, but the difference is that it removes even less tissue from the skull. [6] The term hemispherotomy is now used as an umbrella term to describe the group of modern techniques and procedures that predominate at most contemporary epilepsy centers. [7]

There is no statistically significant difference in seizure-free rates between the four different types of surgeries:  Hemispherotomy, functional hemispherectomy, anatomical hemispherectomy and hemidecortication. The overall rate of seizure freedom is estimated to be 73.4%. [7]   However, hemispherotomy procedures may be associated with a more favorable complication profile. [7]

Candidates

The typical candidates for hemispherectomy are pediatric patients who have intractable epilepsy due to extensive cerebral unilateral hemispheric injuries. [8] [6] In addition, the seizures should ideally be emanating from that same hemisphere. In some situations, a hemispherectomy may still be performed if there are seizures from both hemispheres, as long as the majority come from one side. In order to assess the patient’s epilepsy completely, patients undergo extensive testing, including EEG and MRI. Most patients also undergo other studies including functional MRI (fMRI), positron emission tomography (PET) or magnetoencephalography (MEG).

Today, hemispherectomy is performed as a treatment for severe and intractable epilepsy. The most common underlying etiologies include malformations of cortical development (MCD), perinatal stroke and Rasmussen’s encephalitis. [6] MCD is an umbrella term for a wide variety of developmental brain anomalies, including hemimegalencephaly and cortical dysplasia. Other less common underlying etiologies include hemiconvulsion-hemiplegia epilepsy syndrome and Sturge-Weber syndrome. [7]

Procedure

Patients often shave the area of the scalp that will be involved with the surgery. Patients undergo general anesthesia and are unconscious for the procedure. The surgical site is sterilized, after which the skin is incised. A substantial portion of the bone is removed, followed by incision of the dura, which is the outer covering of the brain. There are several blood vessels that have connections with both sides of the brain, and these are carefully identified and clipped in such a way that spares the healthy hemisphere. Ultimately, a bundle of fibers that connect both of the cerebral hemispheres, the corpus callosum, is removed which results in the functional separation of one hemisphere from the other. Portions of the cerebral lobes from the damaged side of the brain are removed, depending on the specific procedure being performed. The surgeon may leave some brain tissue, such as the thalamus or choroid plexus. After completing the resection, the surgical site is irrigated with saline, the brain covering called the dura is sutured back together, the bone that was removed is replaced and the skin is sutured. This surgery often takes four to five hours. [8] Patients often spend a few nights in the hospital post-operatively, and they undergo physical and occupational therapy soon after the surgery. [8]

Potential complications

The most common complication from surgery is hydrocephalus, a condition in which fluid accumulates within the brain, and this is often treated with a shunt to divert the fluid away. The rate of shunts following surgery ranges from 14-23%. [6] Other complications include wound complications, epidural hemorrhages, subdural hemorrhages, intraparenchymal hemorrhages, intracranial abscesses, meningitis, ventriculitis and venous thrombosis. [7] Additional epilepsy surgery following hemispherectomy is rare (4.5%), [7] but may be recommended if there is a residual connection between the two hemispheres that is causing frequent seizures. Mortality rates are low and estimated to be <1% to 2.2%. [6] [7] Most patients do not experience changes in cognition, but some individuals may be at risk. [7] A visual deficit called contralateral homonymous hemianopsia is expected to occur in most patients, where the entire visual field contralateral to the removed hemisphere is lost. [6] There is a risk of motor deficits, and this is variable. [6] Other possible complications include infection, aseptic meningitis, hearing loss, endocrine problems and transient neurologic deficits such as limb weakness. [6]

Outcomes

Since seizures are the most common indication for hemispherectomy surgery, most research on hemispherectomy analyzes how the surgery affects seizures. Many patients undergoing surgery obtain good surgical outcomes, some obtaining complete seizure freedom (54-90%) and others having some degree of improvement in seizure burden. [6] [7] [9] [10] A recently developed scoring system has been proposed to help predict the probability of seizure freedom with more accuracy:  HOPS (Hemispherectomy Outcome Prediction Scale). [10] Although it cannot definitively predict surgical outcome with exact precision, some physicians may use it as a guide. The scoring system takes certain variables into consideration including age at seizure onset, history of prior brain surgery, seizure semiology and imaging findings.

There is also data pertaining to how hemispherectomy affects the body in other ways. After surgery, the remaining cerebral hemisphere is often able to take over some cognitive, sensory and motor functions. The degree to which the remaining hemisphere takes on this additional workload often depends on several factors, including the underlying etiology, which hemisphere is removed and the age at which the surgery occurs. [11]

In terms of postoperative motor function, some patients may have improvement or no change of their weaker extremity, [9] and many can walk independently. [11] Most patients postoperatively have minimal to no behavioral problems, satisfactory language skills, good reading capability, [11] and only a minority of patients have a decline in IQ. [12] Predictors of poor outcome may include seizure recurrence and structural abnormalities in the intact hemisphere. [11]

Ultimately, risks and benefits should be weighed on an individual basis and discussed in detail with the neurosurgeon. Many patients have excellent outcomes, and the International League Against Epilepsy (ILAE) reports that “about one-fifth of hemispherectomy patients are gainfully employed and even fewer live independently.” [13]

The Brain Recovery Project

The Brain Recovery Project is a non-profit corporation which funds new research and is based in the United States. This corporation hosts an annual two-day conference for patients who have had hemispherectomies and their families. There are several purposes to this reunion. The main goal is to educate patients and their families on the surgery and its necessary subsequent rehabilitation. It also serves as a way for patients and families to connect with one another, learn from specialists in the field and often offers research enrollment. [13]

See also

Related Research Articles

Hemiparesis, or unilateral paresis, is weakness of one entire side of the body. Hemiplegia is, in its most severe form, complete paralysis of half of the body. Hemiparesis and hemiplegia can be caused by different medical conditions, including congenital causes, trauma, tumors, or stroke.

<span class="mw-page-title-main">Neurosurgery</span> Medical specialty of disorders which affect any portion of the nervous system.

Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and peripheral nervous system.

<span class="mw-page-title-main">Split-brain</span> Condition of the human brain

Split-brain or callosal syndrome is a type of disconnection syndrome when the corpus callosum connecting the two hemispheres of the brain is severed to some degree. It is an association of symptoms produced by disruption of, or interference with, the connection between the hemispheres of the brain. The surgical operation to produce this condition involves transection of the corpus callosum, and is usually a last resort to treat refractory epilepsy. Initially, partial callosotomies are performed; if this operation does not succeed, a complete callosotomy is performed to mitigate the risk of accidental physical injury by reducing the severity and violence of epileptic seizures. Before using callosotomies, epilepsy is instead treated through pharmaceutical means. After surgery, neuropsychological assessments are often performed.

The Wada test, also known as the intracarotid sodium amobarbital procedure (ISAP) or Wada-Milner Test, establishes cerebral language and memory representation of each hemisphere.

Corpus callosotomy is a palliative surgical procedure for the treatment of medically refractory epilepsy. In this procedure the corpus callosum is cut through, in an effort to limit the spread of epileptic activity between the two halves of the brain.

Rasmussen's encephalitis is a rare inflammatory neurological disease, characterized by frequent and severe seizures, loss of motor skills and speech, hemiparesis, encephalitis, and dementia. The illness affects a single cerebral hemisphere and generally occurs in children under the age of 15.

<span class="mw-page-title-main">Sturge–Weber syndrome</span> Medical condition

Sturge–Weber syndrome, sometimes referred to as encephalotrigeminal angiomatosis, is a rare congenital neurological and skin disorder. It is one of the phakomatoses and is often associated with port-wine stains of the face, glaucoma, seizures, intellectual disability, and ipsilateral leptomeningeal angioma. Sturge–Weber syndrome can be classified into three different types. Type 1 includes facial and leptomeningeal angiomas as well as the possibility of glaucoma or choroidal lesions. Normally, only one side of the brain is affected. This type is the most common. Type 2 involvement includes a facial angioma with a possibility of glaucoma developing. There is no evidence of brain involvement. Symptoms can show at any time beyond the initial diagnosis of the facial angioma. The symptoms can include glaucoma, cerebral blood flow abnormalities and headaches. More research is needed on this type of Sturge–Weber syndrome. Type 3 has leptomeningeal angioma involvement exclusively. The facial angioma is absent and glaucoma rarely occurs. This type is only diagnosed via brain scan.

Frontal lobe epilepsy (FLE) is a neurological disorder that is characterized by brief, recurring seizures arising in the frontal lobes of the brain, that often occur during sleep. It is the second most common type of epilepsy after temporal lobe epilepsy (TLE), and is related to the temporal form in that both forms are characterized by partial (focal) seizures.

<span class="mw-page-title-main">Electrocorticography</span> Type of electrophysiological monitoring

Electrocorticography (ECoG), a type of intracranial electroencephalography (iEEG), is a type of electrophysiological monitoring that uses electrodes placed directly on the exposed surface of the brain to record electrical activity from the cerebral cortex. In contrast, conventional electroencephalography (EEG) electrodes monitor this activity from outside the skull. ECoG may be performed either in the operating room during surgery or outside of surgery. Because a craniotomy is required to implant the electrode grid, ECoG is an invasive procedure.

Anterior temporal lobectomy (ATL) is the complete or partial removal of the anterior portion of the temporal lobe of the brain. The exact boundaries for removal can vary slightly in practice and between neurosurgeons. It is a treatment option for temporal lobe epilepsy for those in whom anticonvulsant medications do not control epileptic seizures, and who have frequent seizures, and who additionally qualify based on a WADA test to localize the dominant hemisphere for language module.

Epilepsy surgery involves a neurosurgical procedure where an area of the brain involved in seizures is either resected, ablated, disconnected or stimulated. The goal is to eliminate seizures or significantly reduce seizure burden. Approximately 60% of all people with epilepsy have focal epilepsy syndromes. In 15% to 20% of these patients, the condition is not adequately controlled with anticonvulsive drugs. Such patients are potential candidates for surgical epilepsy treatment.

Multiple subpial transections is a surgical treatment modality for epilepsy used in scenarios wherein epileptogenic brain regions cannot be removed safely. The surgeon makes a series of shallow cuts (transections) into the brain's cerebral cortex. These cuts are thought to interrupt some fibers that connect neighboring parts of the brain, but they do not appear to cause long-lasting impairment in the critical functions that these areas perform.

Ohtahara syndrome (OS), also known as early infantile epileptic encephalopathy (EIEE) is a progressive epileptic encephalopathy. The syndrome is outwardly characterized by tonic spasms and partial seizures within the first few months of life, and receives its more elaborate name from the pattern of burst activity on an electroencephalogram (EEG). It is an extremely debilitating progressive neurological disorder, involving intractable seizures and severe intellectual disabilities. No single cause has been identified, although in many cases structural brain damage is present.

Post-traumatic epilepsy (PTE) is a form of acquired epilepsy that results from brain damage caused by physical trauma to the brain. A person with PTE experiences repeated post-traumatic seizures more than a week after the initial injury. PTE is estimated to constitute 5% of all cases of epilepsy and over 20% of cases of acquired epilepsy.

<span class="mw-page-title-main">Epilepsy in children</span>

Epilepsy is a neurological condition of recurrent episodes of unprovoked epileptic seizures. A seizure is an abnormal neuronal brain activity that can cause intellectual, emotional, and social consequences. Epilepsy affects children and adults of all ages and races, it is one of the most common neurological disorders of the nervous system. As well as, this condition is more common among children than adults affecting about 6 out of 1000 US children that are between the age of 0 to 5 years old. The epileptic seizures can be of different types depending on the part of the brain that was affected, seizures are classified in 2 main types partial seizure or genralized seizure.

Cortical stimulation mapping (CSM) is a type of electrocorticography that involves a physically invasive procedure and aims to localize the function of specific brain regions through direct electrical stimulation of the cerebral cortex. It remains one of the earliest methods of analyzing the brain and has allowed researchers to study the relationship between cortical structure and systemic function. Cortical stimulation mapping is used for a number of clinical and therapeutic applications, and remains the preferred method for the pre-surgical mapping of the motor cortex and language areas to prevent unnecessary functional damage. There are also some clinical applications for cortical stimulation mapping, such as the treatment of epilepsy.

Awake craniotomy is a neurosurgical technique and type of craniotomy that allows a surgeon to remove a brain tumor while the patient is awake to avoid brain damage. During the surgery, the neurosurgeon performs cortical mapping to identify vital areas, called the "eloquent brain", that should not be disturbed while removing the tumor.

Drug-resistant epilepsy (DRE), also known as refractory epilepsy, intractable epilepsy, or pharmacoresistant epilepsy, is diagnosed following a failure of adequate trials of two tolerated and appropriately chosen and used antiepileptic drugs (AEDs) to achieve sustained seizure freedom. The probability that the next medication will achieve seizure freedom drops with every failed AED. For example, after two failed AEDs, the probability that the third will achieve seizure freedom is around 4%. Drug-resistant epilepsy is commonly diagnosed after several years of uncontrolled seizures, however, in most cases, it is evident much earlier. Approximately 30% of people with epilepsy have a drug-resistant form.

Musicogenic seizure, also known as music-induced seizure, is a rare type of seizure, with an estimated prevalence of 1 in 10,000,000 individuals, that arises from disorganized or abnormal brain electrical activity when a person hears or is exposed to a specific type of sound or musical stimuli. There are challenges when diagnosing a music-induced seizure due to the broad scope of triggers, and time delay between a stimulus and seizure. In addition, the causes of musicogenic seizures are not well-established as solely limited cases and research have been discovered and conducted respectively. Nevertheless, the current understanding of the mechanism behind musicogenic seizure is that music triggers the part of the brain that is responsible for evoking an emotion associated with that music. Dysfunction in this system leads to an abnormal release of dopamine, eventually inducing seizure.

<span class="mw-page-title-main">Sandi Lam</span> Canadian pediatric neurosurgeon

Sandi Lam is a Canadian pediatric neurosurgeon and is known for her research in minimally invasive endoscopic hemispherectomy for patients with epilepsy. Lam is the Vice Chair for Pediatric Neurological Surgery at Northwestern University and the Division Chief of Pediatric Neurosurgery at Lurie Children's Hospital. She has spent her career advancing pediatric brain surgery capabilities globally through her work in Kenya performing surgeries as well as training and mentoring local residents and fellows.

References

  1. ↑ Dandy, Walter E. (1928-03-17). "REMOVAL OF RIGHT CEREBRAL HEMISPHERE FOR CERTAIN TUMORS WITH HEMIPLEGIA: PRELIMINARY REPORT". Journal of the American Medical Association. 90 (11): 823. doi:10.1001/jama.1928.02690380007003. ISSN   0002-9955.
  2. ↑ McKenzie, KG (1938). "The present status of a patient who had the right cerebral hemisphere removed". JAMA. 111: 168–183.
  3. 1 2 3 Krynauw, R. A. (1950-11-01). "Infantile Hemiplegia Treated by Removing One Cerebral Hemisphere". Journal of Neurology, Neurosurgery & Psychiatry. 13 (4): 243–267. doi:10.1136/jnnp.13.4.243. ISSN   0022-3050. PMC   498647 . PMID   14795238.
  4. 1 2 Rasmussen, Theodore (May 1983). "Hemispherectomy for Seizures Revisited". Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques. 10 (2): 71–78. doi:10.1017/S0317167100044668. ISSN   0317-1671. PMID   6861011.
  5. 1 2 Oppenheimer, D R; Griffith, H B (1966-06-01). "Persistent intracranial bleeding as a complication of hemispherectomy". Journal of Neurology, Neurosurgery & Psychiatry. 29 (3): 229–240. doi:10.1136/jnnp.29.3.229. ISSN   0022-3050. PMC   496024 . PMID   5937637.
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 Lew, Sean M. (July 2014). "Hemispherectomy in the treatment of seizures: a review". Translational Pediatrics. 3 (3): 20817–20217. doi:10.3978/j.issn.2224-4336.2014.04.01. ISSN   2224-4344. PMC   4729844 . PMID   26835338.
  7. 1 2 3 4 5 6 7 8 9 10 Griessenauer, Christoph J.; Salam, Smeer; Hendrix, Philipp; Patel, Daxa M.; Tubbs, R. Shane; Blount, Jeffrey P.; Winkler, Peter A. (January 2015). "Hemispherectomy for treatment of refractory epilepsy in the pediatric age group: a systematic review". Journal of Neurosurgery: Pediatrics. 15 (1): 34–44. doi:10.3171/2014.10.PEDS14155. ISSN   1933-0707. PMID   25380174.
  8. 1 2 3 Fountas, K. N.; Smith, J. R.; Robinson, J. S.; Tamburrini, G.; Pietrini, D.; Di Rocco, C. (August 2006). "Anatomical hemispherectomy". Child's Nervous System. 22 (8): 982–991. doi:10.1007/s00381-006-0135-2. ISSN   0256-7040. PMID   16810492. S2CID   24948589.
  9. 1 2 Peacock, Warwick J.; Wehby-Grant, Monica C.; Shields, W. Donald; Shewmon, D. Alan; Chugani, Harry T.; Sankar, Raman; Vinters, Harry V. (July 1996). "Hemispherectomy for intractable seizures in children: a report of 58 cases". Child's Nervous System. 12 (7): 376–384. doi:10.1007/BF00395089. ISSN   0256-7040. PMID   8869773. S2CID   16491901.
  10. 1 2 Weil, Alexander G.; Lewis, Evan C.; Ibrahim, George M.; Kola, Olivia; Tseng, Chi-Hong; Zhou, Xinkai; Lin, Kao-Min; Cai, Li-Xin; Liu, Qing-Zhu; Lin, Jiu-Luan; Zhou, Wen-Jing; Mathern, Gary W.; Smyth, Matthew D.; O'Neill, Brent R.; Dudley, Roy (May 2021). "Hemispherectomy Outcome Prediction Scale: Development and validation of a seizure freedom prediction tool". Epilepsia. 62 (5): 1064–1073. doi:10.1111/epi.16861. ISSN   0013-9580. PMID   33713438. S2CID   232222766.
  11. 1 2 3 4 Ivanova, Anna; Zaidel, Eran; Salamon, Noriko; Bookheimer, Susan; Uddin, Lucina Q.; de Bode, Stella (November 2017). "Intrinsic functional organization of putative language networks in the brain following left cerebral hemispherectomy". Brain Structure and Function. 222 (8): 3795–3805. doi:10.1007/s00429-017-1434-y. ISSN   1863-2653. PMC   6032986 . PMID   28470553.
  12. ↑ Pulsifer, Margaret B.; Brandt, Jason; Salorio, Cynthia F.; Vining, Eileen P. G.; Carson, Benjamin S.; Freeman, John M. (March 2004). "The Cognitive Outcome of Hemispherectomy in 71 Children". Epilepsia. 45 (3): 243–254. doi:10.1111/j.0013-9580.2004.15303.x. ISSN   0013-9580. PMID   15009226. S2CID   15894321.
  13. 1 2 "The Brain Recovery Project Focuses On Research And Resources After Pediatric Epilepsy Surgery // International League Against Epilepsy". www.ilae.org. Retrieved 2024-02-08.

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