Aura Type Is Useful When Evaluating Candidates for Anterior Temporal Lobectomy

Many patients with temporal lobe epilepsy (TLE) who undergo anterior temporal lobectomy (ATL) become seizure-free, and the benefit can be long-lasting—41% to 53% are still seizure-free 10 years later. Surgical treatment for epilepsy is still underused, though, and it might improve patient uptake to identify factors that predict seizure control.

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Most patients with TLE experience one or more types of aura, and Massachusetts General Hospital researchers recently found aura type is useful to consider when evaluating whether a patient is a candidate for ATL. Ziv M. Williams, MD, a neurosurgeon in the Department of Neurosurgery, and colleagues report the findings in World Neurosurgery.

Methods

The team identified 174 patients who underwent ATL for medically refractory TLE at Mass General between 1993 and 2016 and had at least one year of postoperative follow-up. The average length of follow-up was 7.5 years.

147 of the patients reported having auras before surgery: epigastric (n=59), mnemonic (n=34), cephalic (n=34), somatosensory (n=28), affective (n=28), olfactory (n=19), gustatory (n=19), visual (n=13) and auditory (n=7). These numbers add up to more than 147 because patients who reported multiple aura types were included in each relevant group.

Aura Type and Clinical Variables

Initial univariate analysis identified multiple relationships between clinical factors and specific aura types. After Bonferroni correction, however, the only significant associations were that auditory auras were positively associated with a history of focal-onset impaired-awareness seizures and pathology confined to the lateral temporal cortex and were negatively associated with hippocampal involvement on pathology.

Aura Type and ATL Outcome

Overall, 67% of patients were rated as Engel class I, the most favorable outcome, at their most recent follow-up. Seizure outcome was worse for patients with cephalic auras (53% achieved Engel I) and particularly for those with visual auras (only 38.5% achieved Engel I). 67% of patients without aura achieved Engel I, as did 63% to 82% of patients in other aura groups.

In multivariate analysis:

• Worse Engel class was significantly associated with cephalic auras, gustatory auras, visual auras, and history of tonic–clonic seizures
• Better Engel class was significantly associated with the presence of multiple aura types and fewer antiepileptic drugs used preoperatively

The Influence of Bilateral Seizure Focus

The poor outcome of patients with cephalic, gustatory and visual auras raised the question of whether these auras are associated with bilateral or extratemporal seizure focus. The researchers, therefore, reviewed the results of intracranial electrode monitoring before ATL:

• Cephalic auras—Of 14 patients who underwent monitoring, 11 were found to have unilateral temporal seizure onset. Six of them achieved Engel class I at the most recent follow-up after ATL, whereas one was rated Engel II, two Engel III and two Engel IV. The three other patients had bitemporal seizure activity; one achieved Engel I and two were rated Engel III
• Gustatory auras—All three patients who underwent monitoring had bitemporal seizures; two achieved Engel I and one was rated Engel III
• Visual auras—Of seven patients who underwent monitoring, five had unilateral temporal seizures. One of them achieved Engel I, one was rated Engel II, two Engel III, and one Engel IV. Two patients had bitemporal seizures; one achieved Engel I, and the other was rated Engel III

Selecting Patients for ATL

Aura type thus provides predictive information that can be used to optimize patient workup and selection for ATL:

• Cephalic auras are a poor prognostic factor regardless of the results of invasive monitoring
• Visual auras are also associated with poor seizure outcomes after ATL
• Gustatory auras may be associated with a higher incidence of bitemporal seizure involvement, and patients with this aura type may benefit from invasive monitoring before ATL
• Patients with auditory auras are likely to have excellent ATL outcomes (71% achieved Engel class I), but they may benefit from preoperative intracranial monitoring to determine whether resection of mesial temporal structures is necessary, since they were likely to have only lateral temporal involvement on pathology

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