Children with seizures that stem from the temporal, parietal, and occipital lobes—completely bypassing the central or frontal areas—may be candidates for a surgical procedure called temporoparietaloccipital disconnection or resection (also known posterior quadrantic resection/disconnection). Fewer than 5 percent of all epilepsy surgeries include this procedure, but it’s becoming more common due to improved neuroimaging and pediatric anesthesia.
This procedure targets problematic tissue in the temporal, posterior parietal or occipital lobes of the brain, as often occurs in individuals with cortical dysplasia, Sturge-Weber syndrome, lesions from prenatal stroke, or the consequences of ruptured arteriovenous malformations.
Before the surgery, doctors perform an extensive assessment to determine if the patient is a good fit for the procedure. A child with a visual field defect, but who has good opposite finger control and can tap his/her foot opposite the affected side, are good candidates for posterior quadrantic surgery than hemispherectomy. In general, posterior quadrantic resection is most successful when findings from MRIs, CT scans, nuclear imaging, EEGs and clinical and neuropsychological evaluations all map a brain abnormality to the posterior quadrant.
Just like hemispherectomy, there are generally three different types of posterior quadrantic surgeries: the anatomical posterior quadrantic resection (also known as the TPO resection), the functional poster quadrantectomy (also known as the TPO disconnection), and the peri-insular quadrantectomy. Unlike a hemispherectomy, the posterior quadrantic procedures do not remove the frontal lobe, leaving motor function intact.
During surgery, additional mapping of the brain, known as intraoperative functional mapping, may be done to better define the areas of the brain to be removed. Outcomes are best when the surgeon retains some connection between the rest of the brain and the source of the seizures rather than removing the entire affected region of the brain. In addition, by leaving an intact network of blood vessels to the posterior part of the brain, patients can maintain function of this area.
Long-term seizure outcomes in adults are about 60%, although more studies are needed to characterize outcomes in children. Most patients report improvements in quality of life, cognitive ability and seizure control. Seizure recurrence most often affects children who experience temporal lobe aura, or forced movement or side-gazing eyes when an aura is not present.
Anesthesia issues are the most common surgical complication encountered by young children. These complications are most likely if the patient has health issues such as cavities or loose teeth, enlarged tonsils and adenoids or a heart condition. Seizure medications such as carbamazepine and phenytoin can make people resistant to muscle relaxants and narcotics during sedation. Extensive and continuous monitoring can help reduce these risks.
Sources
Daniel RT, Meagher-Villemure K, Farmer J-P, Andermann F and Villemure J-G. 2007. Posterior Quadrantic Epilepsy Surgery: Technical Variants, Surgical Anatomy, and Case Series. Epilepsia, 48: 1429–1437.
Daniel RT, Babu KS, Jacob R and Villemure J-G. Posterior Quadrantic Resection and Disconnection. In: Cataltepe O, Jallo G, eds. Pediatric epilepsy surgery: Preoperative assessment and surgical treatment. New York: Thieme Medical Publishers, Inc.; 2010.
Davis KL, Murro AM, Park YD, Lee GP, Cohen MJ and Smith JR. 2013. Posterior quadrant epilepsy surgery: predictors of outcome. Seizure. 2012 Nov;21(9):722-8.
Dorfer C, Czech T, Mühlebner-Fahrngruber A, Mert A, Gröppel G, Novak K, Dressler A, Reiter-Fink E, Traub-Weidinger T and Feucht M. 2013. Disconnective surgery in posterior quadrantic epilepsy: experience in a consecutive series of 10 patients. Neurosurg Focus. 2013 Jun;34(6):E10
Hardward S, BS Chen, JD Rolston, MM Haglund and DJ Englot. 2017. Seizure Outcomes in Occipital Lobe and Posterior Quadrant Epilepsy Surgery: A Systematic Review and Meta-Analysis. Neurosurgery, nyx158, https://doi.org/10.1093/neuros/nyx158