What is the management approach for mesial temporal sclerosis?

Management Approach for Mesial Temporal Sclerosis

Surgical resection is the most effective treatment for mesial temporal sclerosis (MTS), achieving long-term seizure freedom in approximately 70% of cases compared to only 25% with pharmacological management alone. 1, 2

Diagnostic Evaluation

• MRI is the initial imaging investigation of choice for suspected MTS, with thin coronal slices through the area of suspected seizure origin, showing higher sensitivity (84%) compared to CT (62%) 3
• FDG-PET shows glucose hypometabolism in MTS cases and can provide additional information when MRI is normal or shows nonspecific findings, with sensitivity of 63-67% 3
• Ictal SPECT can demonstrate hyperperfusion of the epileptogenic region during seizures, while interictal SPECT typically shows hypoperfusion 3
• Subtraction ictal SPECT co-registered to MRI (SISCOM) improves sensitivity and specificity of seizure-related perfusion networks 3

Medical Management

• Initial treatment involves antiepileptic drugs (AEDs), though only about 25% of MTS patients achieve complete seizure control with medication alone 4
• Poor prognostic factors for medical management include early age of seizure onset, history of febrile convulsions, and epileptiform discharges on EEG 4
• The standard length of time given to medical management before considering surgery is typically 2 years, but earlier surgical intervention may be considered when multiple appropriate AEDs fail to establish control 3

Surgical Management

Surgical Options

• Complete surgical resection of the epileptogenic region is the treatment of choice for medically refractory MTS 3
• Two main surgical approaches:
  1. Complete excision of the MTS lesion (lesionectomy)
  2. Complete excision of the MTS lesion together with surrounding epileptogenic tissue (extended resection) 3
• Extended resection has shown higher success rates and low morbidity compared to lesionectomy alone 3
• Temporal lobectomy has demonstrated better seizure outcomes than lesionectomy alone in multiple studies 3

Surgical Outcomes

• Surgery achieves long-term seizure freedom in approximately 70% (62-83%) of MTS cases 1
• Mortality following temporal resection is very rare (<1%) with low rates of definitive neurological complications (1%) 1
• Residual tissue is a significant risk factor for seizure recurrence, emphasizing the importance of complete resection 3
• Seizure outcomes are similar in pediatric and adult populations 1

Alternative Treatments

• Gamma knife stereotactic radiosurgery has shown slightly worse outcomes compared to surgical resection but may provide neuropsychological advantages 1

  • However, there is a latency period of at least 9 months before seizure reduction occurs 1
  • Some patients develop typical radiation changes over time, and persistent seizures may occur 5

• Amygdalohippocampal stimulation can improve seizure control in carefully selected patients who are not candidates for resective surgery 1

• Closed-loop stimulation strategies allow early seizure detection and responsive stimulation, potentially offering less toxic and more effective treatment than continuous neurostimulation 1

• Stereotactic radiofrequency amygdalohippocampectomy is a promising recent approach 1

Factors Affecting Prognosis

• Duration of epilepsy prior to resection does not appear to affect epilepsy outcome 3
• Concordance between multiple diagnostic modalities (MRI, EEG, PET, SPECT) is associated with better surgical outcomes 3
• Complete removal of the epileptogenic zone is critical for optimal seizure control 3

Pitfalls and Caveats

• Not all patients with MTS are medically intractable; approximately 25% can achieve complete control with medication 4
• Surgical treatment remains significantly underutilized despite its proven efficacy 6
• Incomplete resection significantly increases the risk of seizure recurrence and need for reoperation 3
• Functional neuroimaging (PET/SPECT) should be considered when MRI is normal or shows nonspecific findings 3