Vestibular epilepsy is a rare form of epilepsy due to epileptic activity in parts of the cortex that represents the vestibular system. It is often distinctive with sudden, brief episodes of symptoms followed by rapid recovery without sequelae. Known by various terminologies such as epileptic vertigo, vestibular seizures, vertiginous seizures, or epilepsia tornado, it can manifest as an aura to a partial seizure episode or may be the sole manifestation of an epileptic event. It is important to differentiate and characterize epileptic vertigo or dizziness to improve differentiation from nonepileptic causes, particularly when vestibular symptoms are the only apparent manifestations.
The primary objective of this study is to describe the clinical profile of patients with vestibular epilepsy with regard to their clinical presentation, investigations, and subsequent treatment.
MATERIALS AND METHODS
After approval from the institutional research and ethics committee by defibration no. 13039, a retrospective study was done using the medical database of all patients diagnosed with vestibular epilepsy and who presented during the period, January 1, 2014–May 1, 2020, to a neurotology unit of a tertiary care hospital. The medical records of these patients were studied, and their history, neurotological examination, and investigations were noted.
We had a total of 70,049 patients who visited the neurotology clinics of our hospital in the aforementioned period, of which 10 were diagnosed with vestibular epilepsy (prevalence of 0.01%). The age ranged from 9 to 85 years, with a mean age of 29.7 years (standard deviation 7.9) with a 95% confidence interval. Females accounted for 80% of the affected population. The duration of symptoms ranged from 2 months to 48 months, with an average of 8 months.
In all patients, the vertigo attacks were brief, lasting for a few seconds and rarely more than a minute. Six of the individuals described vertigo as a rotation of the surrounding environment, 2 as head rotatory vertigo and 2 could not characterize the vertigo. Six patients (60%) had a loss of consciousness (LOC) along with the dizziness (duration of LOC ranging from 2 min to 2 h). Six patients (numbers 3, 5, 6, 8, 9, and 10) had seizures in the form of abnormal movements of limb with LOC. Fluttering of eyelids was the only symptom before vertigo in a 9-year-old fifth grader.
All patients had a normal otoscopic examination. Four patients had normal hearing, three patients had mild sensorineural hearing loss, one had profound deafness, and two had no documented audiometric tests. All tympanometry was of A type. Three patients had electrocochleography done, of which two showed normal waveforms and patient 1 with profound deafness had no demonstrable peaks [Table 1].
Patient 1 had coexisting Meniere's disease since 1995 and was on betahistine for the same. All individuals with LOC had an echocardiogram (ECHO) and electrocardiogram (ECG) which were normal. Eight patients had a magnetic resonance imaging (MRI) with gadolinium, and the remaining two underwent a plain computerized tomography of the brain. The electroencephalographic (EEG) assessment consisted of routine waking records supplemented by recordings made during hyperventilation and intermittent photic stimulation, and the details of these patients are shown in Table 1.
EEG in patient 8 revealed a generalized epileptiform pattern in frequent paroxysmal bursts of spike and slow-wave discharges seen bilaterally and synchronously, the longest one lasting for a period of 2.5–3 s [Figure 1]. Patient 3 had also had generalized seizures with a frontal predominance [Figure 2]. All patients were started on antiepileptic drugs and had symptomatic relief of their vertigo at 3-month follow-up.
Vestibular epilepsy is characterized by focal seizures with vestibular symptoms as either the sole or predominant feature. It is due to epileptic activity in parts of the cortex that represents the vestibular system and not due to functional loss but the focal discharge that causes vertigo. In a survey of 666 patients of temporal lobe epilepsy, Currie et al. found that 19% of temporal lobe epilepsy presented solely with vertiginous symptoms.
Few, if any, have true rotatory symptoms, and many remain undiagnosed as their symptomatology is purely vestibular. The prevalence of vestibular epilepsy in our neurotology clinic was found to be 0.001%. Most of our patients presented in the second decade of life (7 patients out of 10 were below the age of 25 years). Patients 4 and 10 had a positive paternal history of seizures.
Clinically, none of our patients had nystagmus on examination, with head thrust being positive only in patient 6. Patients 6 and 8 had a sway on Romberg's test with eyes closed and on tandem walking, respectively.
With regard to audiological evaluation, patient 1 had a long-standing history of Meniere's disease for 25 years with bilateral profound hearing loss, and three patients, i.e., 6, 9, and 10, had bilateral minimal hearing loss. Seven patients had electronystagmogram with caloric testing, with 3 of them having bilateral canal paresis, and patients 5 and 10 had left canal paresis. Patient 9 had saccadic intrusions on pendular eye tracking. Patients with epilepsy of an unknown origin were noted to have a hypoactive canal on caloric testing.
Much contention has existed regarding the origin of these seizures as one would regard that seizures with vestibular symptoms should solely originate from the temporal lobe and parietal region which, in turn, receive bilateral inputs.
Vertigo, however, was also believed to be due to the excitability of the parieto-insular cortex area, frontal cortex, intraparietal sulcus, and hippocampus. Subjective feeling of rotation along the pitch plane is mainly noted from activity in the parietal operculum and rotation along the yaw plane from the temporal cortex.
This may explain why patients may present with varying sensorimotor prodromes and may not always present with epileptic nystagmus. Our patients underwent a 1-h EEG with waking records supplemented by recordings made during hyperventilation and intermittent photic stimulation. Five patients had generalized seizure activity, and one had predominant activity in the central and parietal region; however, a systemic review by Tarnutzer et al. showed localized activity frequenting the temporal region (79.8%) and parietal region (11.8%). A closely related condition is reflex epilepsy which refers to seizures occurring due to vestibular, visual, or emotional triggers. None of our patients had epileptic discharges on hyperventilation and photic stimuli, thus ruling out reflex seizures. Another closely related disorder is vestibulogenic seizures which occur due to stimulation of the vestibular system either by peripheral labyrinthine stimulation either during body rotation or caloric testing.
MRI with gadolinium is required to look for any structural cause for origin for epileptic discharge. A normal MRI further supports a diagnosis of vestibular epilepsy. Three patients had abnormal MRI with patient 1, an 85-year-old woman having a chronic right frontal infarct, patient 2 showing nonspecific hyperintensities in the posterior cortex, and patient 6 showing small-vessel ischemic changes. Other techniques employed for assessment, especially in a negative MRI epilepsy scan, are magnetic-encephalography, positron emission tomography, and ictal single-photon emission computed tomography.
All patients with a LOC event had a normal cardiology work. The cardiology tests were tailored to suit the symptoms of each individual and comprised an ECG, an ECHO, a 24-h Holter monitoring, and a head-up tilt table test. None of these patients were found to have a cardiac disease, suggesting that symptoms of spontaneous dizziness with LOC and abnormal limb movements were more likely to be vestibular epilepsy.
To date, no diagnostic criteria have been laid down to diagnose patients with vestibular epilepsy. Diagnosis solely depends on the brief nature of vertigo, an epileptic focus on EEG, negative MRI findings, and a good response to antiepileptic medications.
Vestibular epilepsy responds well to antiepileptics. All our patients in the study were treated with antiepileptic medications as a monotherapy or combined therapy after ruling out other causes [Table 1]. The medications commonly prescribed were levetiracetam and sodium valproate as a monotherapy. An exception is patient 3 who received phenytoin monotherapy and patient 2 who received a combination therapy with clobazam and oxcarbazepine. Most antiepileptics act by stabilizing a hyperactive neuron. Sodium valproate acts by increasing the gamma-aminobutyric acid (GABA) concentration in the brain while clobazam, a benzodiazepine, acts by activation of ligand-gated GABA receptors. Oxcarbazepine stabilizes hyperactive neural membrane by blocking the voltage-gated sodium channels, thereby decreasing the rate of nerve impulse firing, and levetiracetam acts by preventing the propagation of seizure by selectively inhibiting hypersynchronization of epileptiform burst firing.
Many conditions that mimic vestibular epilepsy should be ruled out before starting antiepileptics. Conditions that need to be considered are basilar migraine, vestibulogenic epilepsy, and presyncopal and arrhythmic conditions of cardiac origin.
Vestibular epilepsy is an extremely rare condition (prevalence of 0.01% in a referral neurotology clinic). The diagnosis of vestibular epilepsy should be borne in mind when patients present with short-lived vertigo spells with LOC and not responding to stereotypical regimens. Treatment with anticonvulsants gives a favorable outcome with alleviation of symptoms.
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Conflicts of interest
There are no conflicts of interest.
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