Seizure as the presenting sign of idiopathic intracranial hypertension

Abstract

A 38-year-old man presented to the emergency room with a new generalised tonic-clonic seizure. He also complained of headaches, and brain MRI/magnetic resonance venography (MRV) showed an anterior left temporal encephalocoele with gliosis and brain parenchyma herniating into the left foramen ovale. Ophthalmic examination revealed bilateral optic disc oedema and his lumbar puncture confirmed an elevated opening pressure of 48 cm of water. He was diagnosed with idiopathic intracranial hypertension (IIH) and his papilloedema resolved with weight loss and acetazolamide. Raised intracranial pressure (ICP) can be associated with encephalocoeles and lead to seizures. It is important to screen for papilloedema in these patients as they are at risk for permanent vision loss. This was a unique case in which IIH was diagnosed only after a seizure due to an encephalocoele, which was likely related to chronically undetected raised ICP.

Background

Patients with idiopathic intracranial hypertension (IIH) commonly present with symptoms of raised intracranial pressure (ICP) such as headache, pulsatile tinnitus and vision loss.¹ Common neuroimaging features of IIH include an empty sella, flattening of the posterior globes, tortuosity of the optic nerves sheath and cerebellar tonsillar descent.² Rarer findings include meningocoeles and encephalocoeles, which are a result of bony remodelling from chronically raised ICP leading to herniation of meninges (meningocoele) or brain tissue (encephalocoele).² These findings are strongly associated with cerebrospinal fluid (CSF) leaks, but can also be asymptomatic.² Rarely, encephalocoeles can lead to seizures and are identified on routine brain imaging as part of seizure workup.^{3 4} The goal of this report is to describe a rare occurrence of IIH with undetected papilloedema diagnosed only after seizure. This patient had headaches and papilloedema along with neuroimaging findings of raised ICP and a temporal encephalocoele, which were likely the cause of new onset seizures. Permanent injury to optic nerves and the associated vision loss can be avoided by adequate neuro-ophthalmological evaluation in people with new onset seizures and imaging features of IIH.

Case presentation

A 38-year-old man presented to the emergency room after having a generalised tonic-clonic seizure lasting 10 minutes with loss of consciousness throughout and a postictal period witnessed by his mother. On the day of his seizure, he woke up feeling normal overall and he went outside to smoke cannabis, which he does daily. He came back inside and sat on the couch and then remembered waking up with the emergency medical services present. He was born at term, had a normal development and had no family history of epilepsy. He had a history of a childhood seizure associated with a febrile illness, asthma and obesity (body mass index 35.8 kg/m²). He took salbutamol and fluticasone inhalers for treatment of asthma. He had developed new onset frontotemporal, dull-aching headaches that started several weeks before his seizure. The headaches were mild in intensity (rated 3–4 out of 10 where 0 is no pain and 10 is extreme pain) and present all of the time. There was no associated nausea or vomiting, but occasional photophobia, present a couple of times per week. He also noted constant pulsatile tinnitus in the right ear only that was present for approximately 1 month. He had no visual symptoms. In the emergency room, he had a normal neurological examination.

Investigations

He had an MRI brain that showed two areas of left temporal brain herniation. There was an anterior left temporal encephalocoele with subtle gliosis and the brain parenchyma herniating into the left foramen ovale (figure 1). Moreover, there was an empty sella, tortuosity of the optic nerve sheath and flatting of the posterior sclera—radiological signs of chronically raised ICP (figure 2A, B). Magnetic resonance venogram (MRV) showed distal transverse sinus stenosis (figure 2C). An electroencephalogram was normal. A formal neuro-ophthalmology consultation revealed a visual acuity of 20/20 in both eyes, normal Humphrey 24–2 SITA-Fast visual fields and mild bilateral optic disc oedema (figure 3). Ocular motility and alignment were normal. The average thickness of the retinal nerve fibre layer using optical coherence tomography (OCT) was 115 um OD and 121 um OS. To confirm the diagnosis of IIH, he had a lumbar puncture that demonstrated an opening pressure of 48 cm of water with normal CSF contents.

Figure 1.

(A) Axial T2-weighted MRI of the brain showing a left temporopolar encephalocoele with a tiny area of associated gliosis in the brain parenchyma (arrow). (B, C) Coronal T2-weighted MRI of the brain showing that the left foramen ovale is widened and there is herniation of the brain parenchyma into it.

Figure 2.

(A) MRI of the brain sagittal T1-weighted image showing an empty sella and (B) FLAIR imaging showed floating of the posterior sclera. (C) Magnetic resonance venography showing distal transverse sinus stenosis.

Figure 3.

Optic nerve photos at presentation demonstration bilateral optic disc oedema with peripapillary wrinkles.

Differential diagnosis

The most unifying diagnosis was IIH, which could have resulted in chronic remodelling of the temporal bone and a temporal lobe encephalocoele and associated gliosis. Such temporal gliosis can be a seizure focus. The other possibility is that he could have had a pre-existing bony defect through which the herniation of temporal pole of the brain worsened in context of weight gain and IIH that lead to seizures. Additionally, he could have had an encephalocoele that was unrelated to raised ICP and this patient also had IIH. It is also possible that chronic marijuana use lead to his seizure with incidental findings of IIH and encephalocoele.

Treatment

His seizures were treated with levetiracetam 500 mg two times per day. No loading dose was given and he was maintained on this dose until the final follow-up. He was also treated with acetazolamide 500 mg two times per day and counselled on the importance of weight loss. At final follow-up he reported no further seizure and there was therefore no further imaging follow-up.

Outcome and follow-up

At his 3-month follow-up, he reported a 10 lb weight loss and had no side effects on acetazolamide. His visual acuities were 20/20 in both eyes, there was no optic disc oedema, and had normal Humphrey 24–2 SITA-Fast visual fields. OCT retinal nerve fiber layer (RNFL) thickness also reduced to normal range: 102 um OD and 103 um OS. Therefore, we stopped the acetazolamide. He had no additional seizures on levetiracetam.

Discussion

Patients with IIH commonly present to medical attention after they develop new headaches, pulsatile tinnitus or vision loss. Additionally, papilloedema may be noted as an incidental finding when undergoing routine eye examination for an unrelated reason. Seizures are a very rare presentation of IIH. A recently published retrospective case-control study further characterised the association of IIH with seizures; while still a rare occurrence, non-white individuals with IIH are more likely to have a seizure history than those who are white.⁵ In general, seizures in patients with IIH are attributed to the presence of an encephalocoele. Previous cases have reported that the seizures can be generalised or focal in this clinical context.^{6 7} Patients with epilepsy associated with temporal lobe encephalocoeles may have some neuroimaging findings suggestive of raised ICP, but no clinical signs or symptoms of IIH. Martinez-Poles et al⁴ compared 29 patients with epilepsy and temporal lobe encephalocoeles and 29 patients with epilepsy from other aetiologies. Although the patients with temporal lobe encephalocoeles had a lower pituitary gland height and larger diametre optic nerve sheath, they did not develop typical signs or symptoms of IIH. This suggests that patients with temporal lobe encephalocoeles alone often do not meet the diagnostic criteria for IIH at the time of presentation.

Encephalocoeles are a rare radiological feature of IIH. It is postulated that such brain herniation occurs due to persistently elevated ICP which leads to bone remodelling and the subsequent herniation of neural tissue.^{3 8} We believe it to be the cause of seizures in the case presented. It has also been hypothesised that subsequent intracranial hypotension due to a CSF leak could also contribute to seizures.^{9 10} One study found that 11% of people diagnosed with IIH according to the modified Dandy criteria had meningocoeles on brain imaging compared with 0% of control subjects without IIH.¹¹ In another study, about 50% of patients with either CSF leaks or radiological findings suggestive of IIH had meningocoeles on brain imaging.¹² Thus, it is the recommendation that patients with encephalocoeles should be screened for signs of IIH with a dilated fundus examination to evaluate for papilloedema.¹¹

The association between temporal lobe encephalocoeles and seizures is rare and has been found in less than 5% of cases.¹³ Among patients with refractory temporal lobe epilepsy, 9.6% of patients had a small temporal pole encephalocoele.¹⁴ Furthermore, a larger number of individuals who have refractory epilepsy with temporal encephalocoeles have papilloedema (11.5%) compared with those without encephalocoeles (0.8%), indicative of its usefulness as an assessment tool for the diagnosis of IIH in patients with presentations like this case.¹⁵ However, the presence or absence of encephalocoeles does not provide any additional prognostic information in patients with known papilloedema and IIH. For example, one study indicated that the presence of high-grade papilloedema was comparable in patients with IIH with meningocephalocoeles (25%) to those with IIH without meningocephalocoeles (33%).¹¹ The treatment of seizures related to encephalocoeles from IIH generally involves antiepileptic drugs and treatment of IIH. It is well known that weight loss is the mainstay of IIH treatment along with medical treatment with acetazolamide. In a previous case report, a patient with new onset epilepsy secondary to an encephalocoele and suspected IIH was treated with topiramate; however, despite improvement in their headaches at 18 months, the patient developed five additional convulsions, requiring further increase in the dose of topiramate.⁶

In conclusion, seizures are a rare clinical presentation of IIH. Seizures in patients with IIH are likely secondary to chronic remodelling of the bone and associated brain herniation. In such situations, brain imaging should be carefully evaluated for signs of raised ICP, and the patient should have a dilated fundus exam to look for papilloedema.

Learning points.

• Seizures are a rare presentation of idiopathic intracranial hypertension and could be attributed to the development of encephalocoeles from chronic bone remodelling.

• A patient with an encephalocoele and signs of raised intracranial pressure on neuroimaging should have an eye examination looking for papilloedema.

• Patients with papilloedema and idiopathic intracranial hypertension are at risk for permanent vision loss and require monitoring by an ophthalmologist.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).