Seizures after posterior fossa surgery: Exploring the unknown: A systematic review

Ravish Keni; Luis Rafael Moscote-Salazar; Harsh Deora; GA Quiñones-Ossa; Amit Agrawal

doi:10.4103/am.am_50_20

REVIEW ARTICLE

Year : 2021 | Volume : 18 | Issue : 1 | Page : 16-19

Seizures after posterior fossa surgery: Exploring the unknown: A systematic review

Ravish Keni¹, Luis Rafael Moscote-Salazar², Harsh Deora³, GA Quiñones-Ossa⁴, Amit Agrawal⁵
¹ Department of Neurology, Narayana Medical College and Hospital, Nellore, Andhra Pradesh, India
² Center for Biomedical Research, Faculty of Medicine, University of Cartagena, Cartagena de Indias, Bolivar, Colombia
³ Department of Neurosurgery, NIMHANS, Bengaluru, Karnataka, India
⁴ Faculty of Medicine, El Bosque University, Bogota, Colombia
⁵ Department of Neurosurgery, Narayana Medical College and Hospital, Nellore, Andhra Pradesh, India

Date of Submission	06-Jun-2020
Date of Acceptance	05-Oct-2020
Date of Web Publication	24-Nov-2020

Correspondence Address:
Dr. Amit Agrawal
Department of Neurosurgery, Narayana Medical College Hospital, Chinthareddypalem, Nellore - 524 003, Andhra Pradesh
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/am.am_50_20

Abstract

Background: Seizures due to posterior fossa lesions is an uncommon phenomenon. In this study, a systemic literature review was done to (i) study the incidence of seizures in posterior fossa lesions, (ii) determine factors associated with high risk for seizures, and (iii) ascertain the role of prophylactic antiepileptic drugs (AEDs) in such cases. Methods: Systemic literature review was done, for the MeSH terms “posterior cranial fossa” AND “seizures” AND “anticonvulsants.” All original research articles, case reports, and systematic reviews pertaining to seizures or the use of anticonvulsants in posterior fossa lesions were considered for inclusion. Results: A total of 79 cases of posterior fossa lesions, identified from 8 studies, were included for analysis. The incidence of seizures in posterior fossa lesions ranged from 1.8% to 5% in various studies. The highest incidence for seizures was reported with medulloblastoma, cerebellar hemorrhage, and during microvascular decompression for cases of neurovascular conflict. The most significant risk factor for seizures in the postoperative period was the use of ventricular shunt or ventriculostomy. AEDs were administered symptomatically after the occurrence of seizures in 78 cases except for the use of prophylactic AEDs in a single case of posterior cranial fossa lipoma. Conclusion: Seizures in association with posterior fossa lesions are rare and associated with a poor prognosis. Clinical detection can often be difficult and electroencephalogram helps in early diagnosis and treatment. Further studies are needed to confirm the role of prophylactic AEDs in high-risk cases.

Keywords: Anticonvulsants, posterior cranial fossa, seizures

How to cite this article:
Keni R, Moscote-Salazar LR, Deora H, Quiñones-Ossa G A, Agrawal A. Seizures after posterior fossa surgery: Exploring the unknown: A systematic review. Apollo Med 2021;18:16-9

How to cite this URL:
Keni R, Moscote-Salazar LR, Deora H, Quiñones-Ossa G A, Agrawal A. Seizures after posterior fossa surgery: Exploring the unknown: A systematic review. Apollo Med [serial online] 2021 [cited 2021 Apr 11];18:16-9. Available from: https://www.apollomedicine.org/text.asp?2021/18/1/16/301474

Introduction

The occurrence of seizures in association with supratentorial lesions is well reported and prophylactic antiepileptic drugs (AEDs) are frequently used to reduce seizure recurrence.^{[1],[2],[3],[4],[5]} There is no clear indication that these drugs reduce the incidence of seizures and long-term use is not recommended by most authors.^{[1],[2],[3],[4],[5]} However, seizures due to posterior fossa lesions are an uncommon phenomenon and there is a dearth of literature with regard to this.^[6] The importance of addressing the issue of seizures in posterior fossa lesions is due to the anatomical configuration wherein the posterior fossa being a tight compartment resists even a mild increase in intracranial pressure and can lead to cerebral herniation and threaten life.

In this paper, we did a literature review to (i) study the incidence of seizures in posterior fossa lesions, (ii) determine factors associated with high risk for seizures, and (iii) ascertain the role of prophylactic AEDs in such cases.

Methods

We searched various databases including PubMed, Cochrane, and the grey literature, including relevant organizational websites, for the MeSH terms “posterior cranial fossa” AND “seizures” AND “anticonvulsants.” All original research articles, case reports, and systematic reviews pertaining to seizures or use of anticonvulsants in posterior fossa lesions were considered for inclusion. Excluded were cases having (i) multiple intracranial lesions, (ii) lesions situated in other areas of the brain but were approached through posterior cranial fossa, and (iii) posterior fossa lesions which neither had seizures nor AEDs were used prophylactically.

Results

A total of 79 cases of posterior fossa lesions, identified from 8 studies, who either presented with seizures or in whom AEDs were prophylactically used; were included for analysis. Seizures occurred preoperatively in 15 cases and postoperatively in 63 cases. The various studies dealing with seizures in posterior fossa lesions are summarized in [Table 1].

Table 1: Summary of literature data on seizures in posterior fossa lesions

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Risk of seizures associated the various posterior fossa lesions

Tumors

The most common posterior fossa tumors associated with seizures were medulloblastoma (n = 10, 47%), followed by acoustic neuroma (n = 5, 23.8%). The other tumors less frequently associated with seizures were astrocytoma, meningioma, as well as a rare case of Rosai-Dorfman disease.

Vascular lesions

The most common vascular lesions in the posterior fossa associated with seizures were cerebellar hemorrhage (n = 6, 62.5%), followed by aneurysm (n = 4, 33%). Other lesions were one case each of cerebellar hamartoma and posterior fossa infarction respectively.

Miscellaneous

Other causes of seizures related to posterior fossa lesions were three cases of neurovascular conflict in whom microvascular decompression was attempted and one case of posterior reversible encephalopathy syndrome.

Risk factors for postoperative seizures

The most significant risk factor for seizures in the postoperative period was the use of ventricular shunt or ventriculostomy (n = 20, 50%). The other risk factors were metabolic acidosis, hyponatremia, sepsis, meningitis, use of drugs which predispose to seizures such as cephalosporins, levofloxacin, or bupropion, and operation in a sitting position which predisposed to air embolism and pneumocephalus.

Role of prophylactic antiepileptic drugs

AEDs were administered symptomatically after the occurrence of seizures in 78 cases and prophylactic AEDs were only used in a single case of posterior cranial fossa lipoma.

Outcomes of patients having seizures in posterior fossa lesions

Among the four studies, which looked at patient outcomes in posterior fossa lesions presenting with seizures, poor outcomes were reported in three studies and a single case of cerebellar hamartoma had good outcomes after seizures were controlled.

Discussion

Posterior cranial fossa contains several structures which are pertinent for maintaining a normal level of consciousness. Structural lesion involving the posterior cranial fossa may cause impairment of consciousness commonly by virtue of mass effect leading to raised intracranial pressure and brainstem compression. An important differential diagnosis for the sudden deterioration in the sensorium of patients having posterior fossa lesions is seizure, which may be convulsive or nonconvulsive. Seizures may cause altered consciousness or postictal weakness which may mimic clinical deterioration from other causes. Unlike supratentorial lesions which are commonly associated with seizures, the incidence of seizures in posterior fossa lesions is rarely ranging from 1.8% to 5% in various series.^[6],[7],[12]

The mechanism of seizures in posterior fossa lesions, especially the role played by the cerebellum in controlling epilepsy is a matter of dispute. Dysfunctional cerebellum has been found to be linked with the disinhibition of epileptic activity in the cerebral cortex.^{[14],[15],[16]} Pathologic cerebellar alterations lead to decrease in inhibitory Purkinje cell output to the dentate nucleus and can result in seizures via the excitatory dentatothalamocortical tracts.

The incidence of seizures either pre- or postoperatively is largely dependent upon the type of lesion^{[6],[7],[8],[9],[10],[11],[12],[13]} and use of ventricular shunt or ventriculostomy.^[6],[7] The highest incidence for seizures was reported with medulloblastoma, cerebellar hemorrhage, and during microvascular decompression for cases of neurovascular conflict. The high risk for seizures associated with these entities is plausibly due to breach of the blood–brain barrier and intracranial deposition of hemosiderin, which is considered highly epileptogenic.

Majority of patients with seizures in posterior fossa lesions tend to have poor outcomes.^{[7],[11],[12]} Early detection and prompt administration of AEDs is necessary as seizures can cause cerebral hypoxia, metabolic acidosis, and a further increase in intracranial pressure. However, clinical detection of seizures in posterior fossa lesions is difficult, as convulsive seizures need to be differentiated from decerebrate or decorticate posturing secondary to raised intracranial pressure. Similarly, altered sensorium due to nonconvulsive status epilepticus (NCSE) needs to be differentiated from coma due to structural lesion. Electroencephalogram (EEG) is a vital tool to facilitate seizure diagnosis and initiate prompt treatment. It is mandatory to order continuous EEG monitoring in all patients with posterior fossa lesions who develop altered mental status before or after surgery.

There is no literature evidence regarding the use of prophylactic AEDs or choice of particular AEDs for seizure management.^{[6],[7],[9],[10],[11],[12],[13]} However, in certain cases associated with high risk of seizures as discussed earlier, it is worth considering the possible use of prophylactic AEDs. Prevention of seizures could result in an improved prognosis for such patients. In addition, the use of prophylactic AEDs may also be cost-effective given the increased morbidity and mortality in those patients who do develop seizures and NCSE. Further studies and possibly large-scale multicentric trials are warranted to investigate whether the use of prophylactic AEDs can be recommended in high-risk posterior fossa lesions.

Conclusion

Seizures in association with subtentorial posterior fossa lesions are rare and are associated with a poor prognosis. Clinical detection can often be difficult and EEG helps in early diagnosis and treatment. Further studies are needed to confirm the role of prophylactic AEDs in high-risk cases.

Availability of data and materials

The data that support the findings of this study are available from the corresponding author, (Dr. Agarwal) upon reasonable request.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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