What are the potential complications of functional hemispherotomy in pediatric patients with severe, intractable epilepsy?

Complications of Functional Hemispherotomy

Functional hemispherotomy in pediatric patients with intractable epilepsy carries specific risks including seizure recurrence (requiring reoperation in up to 19% of cases), hydrocephalus requiring shunt placement (occurring in 11-44% depending on technique), infection (meningitis/CSF infection in 5-11%), and motor function deterioration (affecting up to 24% of patients), with bilateral metabolic abnormalities on preoperative FDG-PET serving as the strongest predictor of poor outcomes. 1, 2, 3

Seizure-Related Complications

Seizure Recurrence and Need for Reoperation

• Incomplete disconnection is the primary cause of seizure recurrence, particularly in patients with malformations of cortical development where anatomic complexity may lead to inadequate initial disconnection 2
• Reoperation rates vary by technique: functional hemispherectomy requires completion surgery in approximately 19% of cases (5/27 patients), while anatomic and peri-insular approaches show lower reoperation rates 3
• Bilateral focal metabolic abnormalities on preoperative FDG-PET independently predict seizure recurrence, emphasizing the critical importance of confirming truly unilateral disease before proceeding 1
• Subtle MRI abnormalities extending beyond the disconnected hemisphere or involving the contralateral hemisphere influence surgical outcome and predict recurrence 1

Hydrocephalus and CSF-Related Complications

Ventriculoperitoneal Shunt Requirement

• Hydrocephalus requiring shunt placement is significantly more common with anatomic hemispherectomy (occurring in all 12 patients with developmental malformations who underwent this technique) compared to functional approaches 2
• Functional hemispherectomy shows lower shunt rates (approximately 11% or 3/27 patients) compared to anatomic techniques 2, 3
• Late-onset hydrocephalus can occur years after surgery (reported at 6 years post-procedure), necessitating long-term surveillance 4
• One late death from shunt obstruction has been reported, highlighting the importance of proper shunt management 3

Infectious Complications

Meningitis and CSF Infections

• Mild CSF infections occur in approximately 11% (3/27) of anatomic hemispherectomy patients 3
• Bacterial meningitis without sequelae has been reported following functional hemispherotomy 4
• Bone flap infection requiring operative revision occurs rarely but represents a significant perioperative complication 5

Motor and Functional Complications

Motor Function Changes

• Motor function deterioration affects approximately 24% of patients (12/50), while 76% show improvement or remain unchanged postoperatively 3
• In adult patients, motor function deterioration occurs in 58% (7/12), though patients demonstrate ability to manage postoperative motor impairment even at older ages 5
• Preoperatively hemiparetic extremities may worsen, remain stable, or occasionally improve depending on baseline function and surgical extent 3

Language and Cognitive Function

• Language function remains unchanged in approximately 67% (8/12) of adult patients undergoing the procedure 5
• Cognitive development potential improves when surgery is performed early in appropriate candidates such as hemimegalencephaly and Sturge-Weber syndrome 1

Mortality Risk

Perioperative and Late Mortality

• Intraoperative mortality is rare but documented (1/58 patients in historical series) 3
• Late mortality from complications such as shunt obstruction can occur when managed outside specialized centers 3
• Modern series in adults report no perioperative morbidity or mortality apart from infection requiring revision 5

Critical Pitfalls to Avoid

Preoperative Assessment Errors

• Failing to confirm unilateral disease with FDG-PET preoperatively is the most critical error, as bilateral metabolic abnormalities predict poor outcomes and seizure recurrence 1
• Inadequate evaluation of the contralateral hemisphere's functional integrity leads to unexpected cognitive outcomes 6
• Proceeding without confirming that epileptogenic lesions do not extend beyond the planned disconnection volume results in seizure recurrence 6

Surgical Timing Considerations

• Delaying surgery in appropriate candidates (Sturge-Weber syndrome, hemimegalencephaly, Rasmussen encephalitis) compromises seizure control and cognitive development potential 1
• Early hemisphere disconnection in hemimegalencephaly specifically leads to better seizure control and adequate cognitive development 6

Technical Considerations

• Incomplete disconnection in patients with cortical malformations reflects the anatomic complexity of developmental hemispheric malformations 2
• The absence of background slowing in preoperative EEG, along with ictal and interictal patterns ipsilateral to surgery, associates with favorable outcomes 5