Posterior quadrant disconnection

Posterior quadrant disconnection

Posterior quadrant disconnection (PQD) is surgery for refractory unilateral temporo-parieto-occipital epilepsy to limit the propagation of epileptic discharges. As incomplete disconnection can lead to residual seizures, detailed procedures are presented by Umaba et al. using a cadaveric brain, three-dimensional (3D) reconstruction and simulation models, and intraoperative photographs.

A formalin-fixed adult cadaveric brain was dissected to show each step in PQD. Using 3D preoperative planning software, we reconstructed 3D models from computed tomography and magnetic resonance imaging, and visualized operative views. Intraoperative photographs were taken from the case of a 7-year-old girl with temporo-parieto-occipital epilepsy.

Fronto-temporo-parietal craniotomy is performed. The Sylvian fissure is widely dissected and the insular cortex is exposed. The temporal stem is disconnected along the inferior periinsular sulcus. The disconnection is extended from the limen insulae to the atrium of the lateral ventricle (LV). The fibers between the head of the hippocampus and the amygdala are disconnected. The parietal lobe is disconnected along the postcentral sulcus and the disconnection is connected to the atrium of the LV. At the medial surface of the parietal lobe, the disconnection is continued until reaching the corpus callosum (CC). The splenium of the CC is disconnected via the medial wall of the LV. The fornix is divided in the atrium of the LV. After these steps, disconnection of the unilateral tempo-parieto-occipital lobe is achieved while preserving the arteries and veins.

Inclusion of views from cadaveric brains, 3D reconstruction and simulation models, and intraoperative photographs facilitates a clearer anatomical understanding of PQD 1).

Twenty hemispheres were dissected according to Klingler’s fiber dissection technique illustrating the peri-insular (temporal stem, superior longitudinal fasciculus, corona radiata) and mesial disconnection (mesiotemporal cortex, cingulum, and corpus callosum).

Extensive white matter tract disconnection is obtained after posterior quadrant disconnection. Callosal fibers connecting the anterior most part of the parietal cortex invariably ran through the isthmus of the corpus callosum and need to be disconnected, while frontal lobe connections including the corticospinal tract and the anterior two-thirds of the corpus callosum are spared during the procedure.

The findings suggest the involvement of both the splenium and the isthmus in interhemispheric propagation in posterior cortex epilepsies. Sectioning the total extent of the posterior one-third of the corpus callosum might therefore be necessary to achieve optimal outcomes in posterior quadrant epilepsy surgery 2).

Nooraine et al. analyzed the data of seven (n = 7) consecutive posterior quadrant epilepsy patients who underwent posterior quadrant disconnection with a mean age of 8.5 years over the last three years of which 4 were male and 3 females. All patients underwent extensive pre-surgical evaluation including detailed history, examination, prolonged video EEG recordings, neuropsychological testing, MRI brain, DTI, PET scan (n = 6), fMRI (n = 4), WADA test (n = 1) and invasive recording (n = 1), Of seven patients four had left sided pathology and three had right sided pathology. All patients except one underwent pure disconnection and one underwent partial resection.

Posterior quadrant disconnection is effective surgical procedure for medically refractory epilepsy arising from the posterior quadrant in carefully selected patients without morbidity or functional disability across various age groups especially in children. In our series, all seven patient had good seizure outcome and none had functional disabilities 3).

Ten patients who were surgically treated using the posterior quadrantectomy (PQT) were enrolled in this study. Surgical outcome was analyzed as seizure-free or not at 2 years after surgery. Psychomotor development was evaluated by the scores of mental developmental index (MDI) and psychomotor developmental index (PDI) in the Bayley Scales of Infant Development II preoperatively, and at 6 and 12 months after the PQT. RESULTS:

Eight of 10 patients were seizure-free. Patients without complete elimination of the angiomatous areas had residual seizures. Average MDI and PDI scores before the surgery were 64.8 and 71.6, respectively. Scores of MDI at 6 and 12 months after the PQT in seizure-free patients were 80.5 and 84.5, respectively (p < 0.01). PDI scores at these postoperative intervals were 87.3 and 86.4, respectively (p < 0.05). Patients with residual seizures did not improve in either MDI or PDI. SIGNIFICANCE:

The PQT achieved good seizure control and improved psychomotor development in patients with SWS. The complete deafferentation of angiomatous areas is required for seizure-free results and psychomotor developmental improvement 4).

There were 3 males and 7 females (median age 8.7 years; range 4.2-22.1 years). The affected hemisphere was the left in 3 patients and the right in 7. The patients’ median age at seizure onset was 3.0 years (range 0.2-8.3 years). The median duration of epilepsy before surgery was 5.2 years (range 1.3-17.2 years). The underlying pathology was TPO malformation of cortical development in 5 patients, and venous infarction, posterior hemispheric quadrant atrophy, Sturge-Weber syndrome, cortical involvement of a systemic lupus erythematosus, and gliosis after cerebral tumor treatment in 1 each. In 6 children, a pure TPO disconnection was performed; in 2 patients, the temporal lobe was resected and parietooccipital disconnection was performed. The 2 remaining patients had had previous epilepsy surgery that was extended to a TPO disconnection: disconnection of the occipital lobe (n = 1) and resection of the temporal lobe (n = 1). The authors encountered no complications while performing surgery. No patient needed blood replacement therapy. No patient developed CSF disturbances that warranted treatment. Nine of 10 patients are currently seizure free since surgery (Wieser Class 1a) at a median follow-up time of 2.1 years (range 4 months to 8.1 years). CONCLUSIONS:

Temporoparietooccipital disconnection is a safe and effective motor-sparing epilepsy surgery in selected cases. Technical adjuncts facilitate a better intraoperative visualization and orientation, thereby enabling a less invasive approach than previously suggested 5).

there were 13 patients with a median age of 17 years. All patients had extensive presurgical evaluation that provided concordant evidence localizing the lesion and seizure focus to the posterior quadrant. The objective of the surgery was to eliminate the effect of the epileptogenic tissue and preserve motor and sensory functions. RESULTS:

During the course of this study period of 15 years, the surgical procedure performed evolved toward incorporating more techniques of disconnection and minimizing resection. Three technical variants were thus utilized in this series, namely, (i) anatomical posterior quadrantectomy (APQ), (ii) functional posterior quadrantectomy (FPQ), and (iii) periinsular posterior quadrantectomy (PIPQ). After a median follow-up period of 6 years, 12/13 patients had Engel’s Class I seizure outcome. CONCLUSION:

The results of surgery for posterior quadrantic epilepsy have yielded excellent seizure outcomes in 92% of the patients in the series with no mortality or major morbidity. The incorporation of disconnective techniques in multilobar surgery has maintained the excellent results obtained earlier with resective surgery 6).

An enhanced operative video presents the illustrative case of a total Posterior quadrant disconnection indicated for a 15-year-old boy with Sturge-Weber syndrome suffering from seizure recurrence after a partial PQD. Barrit et al. described the surgical procedure with emphasis on relevant anatomy and multimodal intraoperative guidance in three steps: (i) parieto-occipital disconnection, (ii) posterior callosotomy, and (iii) temporal disconnection/resection. Pearls and pitfalls of surgical management are discussed.

Posterior quadrant disconnection is a less invasive surgical option than typical hemispherectomy for selected indications of posterior multilobar epilepsy 7).


Umaba R, Uda T, Nakajo K, Kawashima T, Tanoue Y, Koh S, Uda H, Kunihiro N, Matsusaka Y, Ohata K. Anatomical understanding of posterior quadrant disconnection from cadaveric brain, 3D reconstruction and simulation model, and intraoperative photographs. World Neurosurg. 2018 Aug 30. pii: S1878-8750(18)31951-X. doi: 10.1016/j.wneu.2018.08.168. [Epub ahead of print] PubMed PMID: 30172981.

Verhaeghe A, Decramer T, Naets W, Van Paesschen W, van Loon J, Theys T. Posterior Quadrant Disconnection: A Fiber Dissection Study. Oper Neurosurg (Hagerstown). 2018 Jan 1;14(1):45-50. doi: 10.1093/ons/opx060. PubMed PMID: 29253283.

Nooraine J, R SK, Iyer RB, Rao RM, Raghavendra S. Posterior quadrant disconnection for refractory epilepsy: A case series. Ann Indian Acad Neurol. 2014 Oct;17(4):392-7. doi: 10.4103/0972-2327.144006. PubMed PMID: 25506159; PubMed Central PMCID: PMC4251011.

Sugano H, Nakanishi H, Nakajima M, Higo T, Iimura Y, Tanaka K, Hosozawa M, Niijima S, Arai H. Posterior quadrant disconnection surgery for Sturge-Weber syndrome. Epilepsia. 2014 May;55(5):683-9. doi: 10.1111/epi.12547. Epub 2014 Feb 22. PubMed PMID: 24621276.

Dorfer C, Czech T, Mühlebner-Fahrngruber A, Mert A, Gröppel G, Novak K, Dressler A, Reiter-Fink E, Traub-Weidinger T, Feucht M. Disconnective surgery in posterior quadrantic epilepsy: experience in a consecutive series of 10 patients. Neurosurg Focus. 2013 Jun;34(6):E10. doi: 10.3171/2013.3.FOCUS1362. PubMed PMID: 23724834.

Daniel RT, Meagher-Villemure K, Farmer JP, Andermann F, Villemure JG. Posterior quadrantic epilepsy surgery: technical variants, surgical anatomy, and case series. Epilepsia. 2007 Aug;48(8):1429-37. Epub 2007 Apr 18. PubMed PMID: 17441997.

Barrit S, Park EH, Madsen JR. Posterior quadrant disconnection for refractory epilepsy: how I do it. Acta Neurochir (Wien). 2022 May 17. doi: 10.1007/s00701-022-05221-x. Epub ahead of print. PMID: 35578117.

Hemispherectomy for Rasmussen’s encephalitis

Hemispherectomy for Rasmussen’s encephalitis

Compared with functional hemispherectomy and hemisphere disconnection, anatomical hemispherectomy elicited better seizure outcomes with an acceptable level of complications. Early-stage operations might lead to better cognitive status, but they are associated with a high risk of IQ decline 1).

Obtaining complete disconnection is critical for favorable seizure outcomes from hemispherectomy, and neurosurgeons should have a low threshold to reoperate in patients with Rasmussen’s encephalitis with recurrent seizures. Rapid progression of motor deficits and bilateral MRI abnormalities may indicate a subpopulation of patients with RE with an increased risk of needing reoperation. Overall, they believe that hemispherectomy is a curative surgery for the majority of patients with RE, with excellent long-term seizure outcome2).

The majority of pediatric patients undergoing resection or hemispherectomy for RE achieve good seizure outcome. Although small retrospective cohort studies are inherently prone to bias, the best available evidence utilizing individual participant data suggests hemispheric surgery and younger age at the surgery are associated with good seizure outcomes following epilepsy surgery. Large, multicenter observational studies with long-term follow-up are required to evaluate the risk factors identified in a review 3).

Hemispherotomy remains the gold standard treatment but causes permanent functional impairment. No standardized medical treatment protocol currently exists for patients prior to indication of hemispherotomy, although some immunotherapies have shown partial efficacy with functional preservation but poor antiseizure effect. Some studies suggest a role for tumor necrosis factor alpha (TNF-α) in RE pathophysiology.


Guan Y, Chen S, Liu C, Du X, Zhang Y, Chen S, Wang J, Li T, Luan G. Timing and type of hemispherectomy for Rasmussen’s encephalitis: Analysis of 45 patients. Epilepsy Res. 2017 May;132:109-115. doi: 10.1016/j.eplepsyres.2017.03.003. Epub 2017 Mar 22. PMID: 28399506.

Sundar SJ, Lu E, Schmidt ES, Kondylis ED, Vegh D, Poturalski MJ, Bulacio JC, Jehi L, Gupta A, Wyllie E, Bingaman WE. Seizure Outcomes and Reoperation in Surgical Rasmussen Encephalitis Patients. Neurosurgery. 2022 May 13. doi: 10.1227/neu.0000000000001958. Epub ahead of print. PMID: 35544031.

Harris WB, Phillips HW, Chen JS, Weil AG, Ibrahim GM, Fallah A. Seizure outcomes in children with Rasmussen’s encephalitis undergoing resective or hemispheric epilepsy surgery: an individual participant data meta-analysis. J Neurosurg Pediatr. 2019 Dec 6:1-10. doi: 10.3171/2019.9.PEDS19380. [Epub ahead of print] Review. PubMed PMID: 31812145.

American Society for Stereotactic and Functional Neurosurgery

American Society for Stereotactic and Functional Neurosurgery

Magnetic resonance image-guided laser interstitial thermal therapy (MRgLITT) is a tool in the neurosurgical armamentarium for the management of drug-resistant epilepsy. Given the introduction of this technology, the American Society for Stereotactic and Functional Neurosurgery (ASSFN), which acts as the joint section representing the field of stereotactic and functional neurosurgery on behalf of the Congress of Neurological Surgeons and the American Association of Neurological Surgeons, provides here the expert consensus opinion on evidence-based best practices for the use and implementation of this treatment modality. Indications for treatment are outlined, consisting of failure to respond to, or intolerance of, at least 2 appropriately chosen medications at appropriate doses for disabling, localization-related epilepsy in the setting of well-defined epileptogenic foci, or critical pathways of seizure propagation accessible by MRgLITT. Applications of MRgLITT in mesial temporal lobe epilepsy and hypothalamic hamartoma, along with its contraindications in the treatment of epilepsy, are discussed based on current evidence. To put this position statement in perspective, they detailed the evidence and authority on which this ASSFN position statement is based 1)

A persistent underuse of epilepsy surgery exists. Neuromodulation treatments including deep brain stimulation (DBS) expand the surgical options for patients with epilepsy and provide options for patients who are not candidates for resective surgery. DBS of the bilateral anterior nucleus of the thalamus is an Food and Drug Administration-approved, safe, and efficacious treatment option for patients with refractory focal epilepsy. The purpose of this consensus position statement is to summarize evidence, provide recommendations, and identify indications and populations for future investigation in Deep Brain Stimulation for epilepsy. The recommendations of the American Society for Stereotactic and Functional Neurosurgery are based on several randomized and blinded clinical trials with high-quality data to support the use of DBS to the anterior nucleus of the thalamus for the treatment of refractory focal-onset seizures.

Cabrera et al. designed a 51-question online survey comprising Likert-type, multiple-choice, and rank-order questions and distributed it to members of the American Society for Stereotactic and Functional Neurosurgery (ASSFN). Descriptive and inferential statistical analyses were performed on the data.

They received 38 completed surveys. Half (n = 19) of responders reported devoting at least a portion of their clinical practice to psychiatric neurosurgery, utilizing DBS and treating obsessive compulsive disorder (OCD) most frequently overall. Respondents indicated that psychiatric neurosurgery is more medically effective (OR 0, p = 0.03242, two-sided Fisher’s exact test) and has clearer clinical indications for the treatment of OCD than for the treatment of depression (OR 0.09775, p = 0.005137, two-sided Fisher’s exact test). Seventy-one percent of all respondents (n = 27) supported the clinical utility of ablative surgery in modern neuropsychiatric practice, 87% (n = 33) agreed that ablative procedures constitute a valid treatment alternative to DBS for some patients, and 61% (n = 23) agreed that ablative surgery may be an acceptable treatment option for patients who are unlikely to comply with postoperative care.

This up-to-date account of practices, perceptions, and predictions about psychiatric neurosurgery contributes to the knowledge about evolving attitudes over time and informs priorities for education and further surgical innovation on the psychiatric neurosurgery landscape 2).


2016 Biennial Meeting of the American Society for Stereotactic and Functional Neurosurgery, Chicago, IL, USA, June 18-21, 2016: Abstracts 3)


Wu C, Schwalb JM, Rosenow JM, McKhann GM 2nd, Neimat JS; American Society for Stereotactic and Functional Neurosurgeons. The American Society for Stereotactic and Functional Neurosurgery Position Statement on Laser Interstitial Thermal Therapy for the Treatment of Drug-Resistant Epilepsy. Neurosurgery. 2022 Feb 1;90(2):155-160. doi: 10.1227/NEU.0000000000001799. PMID: 34995216.

Cabrera LY, Courchesne C, Kiss ZHT, Illes J. Clinical Perspectives on Psychiatric Neurosurgery. Stereotact Funct Neurosurg. 2019;97(5-6):391-398. doi: 10.1159/000505080. Epub 2020 Jan 17. PMID: 31955163.

2016 Biennial Meeting of the American Society for Stereotactic and Functional Neurosurgery, Chicago, IL, USA, June 18-21, 2016: Abstracts. Stereotact Funct Neurosurg. 2017 Jan 16;94 Suppl 2:1-77. doi: 10.1159/000455386. [Epub ahead of print] PubMed PMID: 28092908.
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