Besides being associated with mucocutaneous infections, herpes simplex virus (HSV) is the most common cause of viral encephalitis. The brain lesions in HSV encephalitis (HSVE) primarily involve the temporal and frontal lobes. About half of patients develop seizures, which may progress to chronic seizure disorders or status epilepticus.
Antiepileptic medications are the primary method to control or prevent seizures in HSVE. Still, surgery can be an important adjuvant treatment in severe cases, mainly decompressive procedures to treat elevated intracranial pressure (ICP).
In Neurosurgery, physicians at Brigham and Women’s Hospital recently described only the second case in which anterior temporal lobectomy (ATL) was used to manage status epilepticus in a patient with HSVE. They present the largest systematic review that addresses whether neurosurgery has a beneficial effect on outcomes in HSVE.
The authors are Varun M. Bhave, BA, Joshua D. Bernstock, MD, PhD, clinical fellow in the Department of Neurosurgery, Saef Izzy, MD, critical care neurologist in the Department of Neurology, G. Rees Cosgrove, MD, director of Epilepsy and Functional Neurosurgery in the Department of Neurosurgery, and colleagues.
A 52-year-old woman with HSVE developed medically refractory right temporal lobe seizures. Despite a decompressive hemicraniectomy on hospital day 9 and a three-week course of acyclovir, she developed non-convulsive status epilepticus that did not respond to continued antiepileptic drug therapy.
On hospital day 28, on the recommendation of a multidisciplinary surgical epilepsy conference, ATL was performed with resection of the right lateral temporal neocortex and medial temporal structures, including the uncus, amygdala, and anterior hippocampus. Postoperative continuous EEG through hospital day 65 revealed no evidence of additional seizures.
The patient was discharged to rehabilitation on hospital day 73. At the time of this writing, approximately eight months later, she demonstrated moderate disability (Glasgow Outcome Scale 4). She could communicate fluently, ambulate unassisted, and perform activities of daily living with minimal assistance. She continued cenobamate and oxcarbazepine and had not experienced any additional seizures.
The previous case of using ATL to manage status epilepticus in a patient with HSVE involved a 60-year-old man who also achieved resolution of seizures with minimal functional impairment. He underwent right ATL approximately three weeks after the illness onset.
In June 2022, the Brigham team searched PubMed and Google Scholar for case reports and case series about neurosurgical intervention for acute HSVE. The review identified 54 papers, published between 1967 and 2020, that incorporated 67 patients (48% female, 26% pediatric).
Scope of surgery
64 of the 67 patients who underwent surgery for HSVE-associated seizures also had radiologic evidence of severely elevated ICP:
- Decompressive craniectomy with or without concurrent temporal lobectomy was reported in 46 cases (72%)
- Temporal or frontal lobectomy without craniectomy was reported for surgical decompression in the other 18 cases (28%)
- Elevated ICP in HSVE often results from diffuse cerebral edema, but 12 of the 64 patients (19%) developed frank hemorrhage that required surgical evacuation
Timing of surgery
Surgical decompression was reported at a wide range of times after symptom onset, from day 1 to day 25 of illness. However, 52 of the 53 patients with sufficient documentation underwent initial decompressive surgery at least four days after symptom onset. Only two patients underwent initial decompression more than three weeks after symptom onset.
Outcomes were recorded in 61 cases of decompressive surgery:
- 35 patients (57%)—Low long-term disability and resolved or nondisabling residual neurological deficits (whether surgery was performed within 10 days or after more protracted periods of HSVE symptoms)
- 12 patients (20%)—In-hospital mortality
- 14 patients (23%)—Moderate to severe long-term functional disability
The case report and review suggest the following about taking care of patients with acute HSVE:
- The timing of elevated ICP may be difficult to predict, so vigilance is warranted throughout a patient’s hospital course
- Surgical decompression can become necessary despite prompt initiation of appropriate antiviral therapy
- ATL should be considered for patients who have focal status epilepticus or refractory seizures of unilateral origin