Currently, multiple strategies for disconnecting parts of the brain have gained wide acceptance in epilepsy surgery centers, mostly due to the fact that, in children, extratemporal epilepsies are far more common than temporal ones (in contrast with adults) and that the most common pathological substrate in this age group is cortical dysplasia, which usually displays wider epileptogenic areas. Additionally, in comparison with the larger resections traditionally used, disconnective surgery has the advantage of lower complication rates but with similar seizure and functional outcomes. In this chapter, the authors have divided cerebral disconnection into anterior (frontal disconnection), posterior quadrantic (temporo-parieto-occipital or parieto-occipital disconnection), and hemispheric (hemispherotomy) and discussed surgical anatomy and techniques in detail.
18.1 Introduction
The term “disconnective surgery” refers to a number of surgical procedures performed to isolate broad epileptogenic zones (EZs), most often encompassing a whole or multiple cerebral lobes.1, 2, 3, 4These operations have a particular importance for children, in whom extratemporal epilepsy is very common (comprising up to 20–30% of surgical procedures in the pediatric age group).5, 6Nevertheless, seizure freedom is less likely to be achieved in such cases, but careful patient selection and presurgical workup, alongside a meticulous surgical technique, can surely improve outcome of such resections.6, 7
The goal of this chapter is to provide a review of the relevant anatomy and techniques used in cerebral disconnective surgery for the treatment of refractory epilepsy. Obviously, the most effective strategy is a focal cortical resection with full excision of the EZ.5However, this might be hard to achieve in some patients, whose epilepsy may be widespread within the frontal, parietal, and occipital lobes. In such cases, extended surgery is required. Especially in children, disconnective procedures are currently preferable to traditional lobectomies as they reduce complications related to extensive resections, such as massive blood loss, hydrocephalus, and longer operating times, while achieving equivalent seizure outcomes.8Complete disconnection of the epileptogenic cortex from the surrounding brain tissue and downstream midbrain is sufficient for controlling seizures, even if the pathological substrate is left in situ.7, 8
18.2 Preoperative Evaluation Workup
A thorough preoperative clinical assessment is quintessential for successful disconnective surgery. It should provide the surgical team with anatomical and functional information required for outlining of the disconnection area, and for avoidance of postoperative neurological deficits. To achieve this, nuclear medicine tests, high-resolution imaging, and electrophysiological techniques must be available.
An ideal preoperative protocol includes a detailed clinical and neurological assessment, scalp electroencephalography (EEG); brain magnetic resonance (MR—3T) scans; ictal and interictal video EEG; neuropsychological and psychiatric evaluation; social worker assessment; and, in selected cases, ictal and interictal single-photon emission computed tomography (SPECT) coregistered to MR (SISCOM), positron emission tomography (PET), functional MR, invasive monitoring (with subdural and depth electrodes), and Wada test.
18.3 Indications for Surgery
Disconnective surgery is indicated after medical refractoriness of the patient’s epilepsy is established and when there is consonance of clinical and EEG findings; for instance, frontal epilepsy is usually clinically manifested by tonic/clonic seizures (reflecting involvement of Brodmann area 6 or 4), hypermotor seizures, or dialeptic/autonomic seizures1, 9(▶Fig. 18.1), whereas focal seizures with unilateral temporo-parieto-occipital (TPO) onset or generalized seizures with asymmetrical clinical or electroencephalographic features suggest a focal origin on the TPO region10(▶Fig. 18.2, ▶Fig. 18.3). Also, the presence of a unilateral lesion identifiable on MR scans or functional imaging and the absence of hemispheric lesions (which would require hemispherotomy) are important prerequisites for disconnective surgery.10, 11, 12
Fig. 18.1 A 5-year-old boy with seizures since 6 months of age, refractory to antiepileptic drugs (AED), mild cognitive delay, and diagnosed with tuberous sclerosis complex (TSC). Magnetic resonance (MR) scans in a, c, and d showing multiple tubers. (b) Intraoperative photograph showing the tubers in the frontal region. Surgery: right frontal disconnection + resection of frontal tuber. (e) Photograph depicting the cortical incision along the disconnected frontal lobe. (f and g) Post-op computerized tomographic (CT) scan showing the frontal disconnection. The patient is seizure free postoperatively.Fig. 18.2 A 1-year 8-month-old boy, with cognitive delay, left motor deficit, mainly hand weakness. Antenatal (gestational) seizures, refractory to AED, evolving to up to 50 seizures per day. Video EEG: focal status epilepticus in the posterior quadrant. (a–e) MR scans showing typical aspects of hemimegalencephaly. Surgery: posterior quadrantic disconnection. (f and g) Intraoperative pictures of the brain before and after disconnection, respectively. He is seizure free 4 years after surgery. Left hemiparesis persisted, but he is able to walk independently. Improved cognition and language. (h–j) Postoperative MR 1 year after surgery. Pathology: CD type IIb (hemimegalencephaly).Fig. 18.3 An 18-year-old girl, with seizures since the age of 2 years and 6 months. Semiology: hypotonic seizures with head drop. Seizures improved for 5 years, then recurred in the form of generalized paresthesias, staring, cephalic flexion, and loss of consciousness. They were very frequent (around 60 per day), sometimes in clusters. Refractory to AEDs. Video EEG demonstrated EZ located in the left posterior quadratic region. Ictal SPECT and PET were not helpful. (a–d) MR was normal and functional MR confirmed language area in the left hemisphere. (e and f) Chronic monitoring confirmed EZ in the left posterior region. (g–i) Reconstructions showing the surgical disconnection line. Surgery: parieto-occipital disconnection. Pathology: CD type IIa. She is seizure free postoperatively.
In children, cortical dysplasia (CD) is the main pathological indication for surgery. Although type II CD is more frequent, type I CD can also be seen among these cases. Eventually, some of these cases will turn into hemispherotomy (▶Fig. 18.4, ▶Fig. 18.5), due to persistence of seizures after localized disconnections. Another good indication for surgery is asymmetric hemimegalencephaly, predominantly in the frontal lobe or in the posterior quadrant.13Furthermore, there are some other typical clinical scenarios in pediatric epilepsy in whom disconnective surgical procedures are recommended, such as ischemic, traumatic, or vascular lesions (▶Fig. 18.5), and tuberous sclerosis complex (TSC; ▶Fig. 18.1) or Sturge–Weber syndrome (▶Fig. 18.6, ▶Fig. 18.7) cases with preserved motor function but more widespread epileptogenicity.
Fig. 18.4 An 11-year-old boy, with seizures since the age of 2 years. Semiology: generalized tonic–clonic with cyanosis, very frequent (>110/day), refractory to AED. Infantile spasms and drop attacks. Significant cognitive delay. Video EEG was consistent with epileptic encephalopathy and Lennox-Gastaut syndrome but failed to define the EZ. (a–c) MR scans showing blurring of the right frontal region. Surgery: frontal disconnection. Pathology: CD type IIa. (d–f) Postoperative MR scans showing the frontal disconnection. Patient experienced a substantial clinical improvement for 8 months. Afterward, seizures recurred with the same semiology and frequency. He subsequently underwent hemispherotomy. (g) Postoperative MR showing complete disconnection of the hemisphere and mild ischemic injury in the parietal and temporal lobes. He is seizure free postoperatively.Fig. 18.5 A 2-year-old boy presenting with seizures since the age of 9 months, after traumatic brain injury (fall). Seizures were refractory to AEDs, several times a day, manifested as infantile spasms, head drop, and sometimes lateralized to the left. Left-sided weakness. Video EEG: epileptogenic zone located in the posterior quadrant of the right hemisphere. (a and b) Preoperative MR showing right hemispheric atrophy with considerable preservation of the central region. (d and e) Postoperative MR shows complete disconnection of the right posterior quadrantic region. (c) Surgical aspect of the brain, with atrophy mainly in the frontal region. Blue string showing the programmed disconnection (hand area—blue circle). He was seizure free for a month only; seizures relapsed with same semiology. A final clinical decision was to perform hemispherotomy, 1 year after the first operation. Patient is seizure-free at 1-year follow-up consultation.Fig. 18.6 A 5-year-old girl, diagnosed with Sturge–Weber syndrome and refractory epilepsy but no motor deficits. Right facial hemangioma (port wine stain), mild mental retardation. Family was unwilling to accept any postoperative motor deficits. (a) CT scan showing calcifications in the right hemisphere. (b and c) MR scans depicting an atrophic right hemisphere with a contrast-enhanced arachnoid surface. (d) Schematic representation of the pial angiomas. (e) Surgical photograph showing the extension of the angioma and the gap in the central area.Fig. 18.7 (a) Cortical map after invasive monitoring showing the epileptogenic zone anterior (more prominent) and posterior to the central region. (b and c) Initial surgical strategy was a frontal disconnection, depicted in the MR. After surgery, seizures recurred within a few months, with the same semiology. In order to preserve motor function, the final decision was to propose a combined disconnection, including a posterior disconnection associated with the previous frontal one. (d) Schematic representation of the final operation preserving the central lobe. The patient is seizure free and with no motor deficits on follow-up. (e) CT scan showing the preservation of the central area.
Only gold members can continue reading. Log In or Register to continue
