Abstract
Perriguey M, Elziere M, Lopez C, Bartolomei F. J Neurol. 2024;272(1):68. doi:10.1007/s00415-024-12796-1. PMID: 39680238. Background: Focal seizures may encompass vestibular sensations in their symptomatology. When these manifestations occur in isolation or constitute the predominant symptom, they prompt consideration for diagnosing recurrent paroxysmal vertigo. However, the characterization of “vestibular epilepsy” remains debated and underexplored. Our objective is to characterize the clinical and electrophysiological criteria of vestibular epilepsy. Methods: We retrospectively analyzed data from a cohort of outpatients treated in the epileptology department of Marseille University Hospital. The study focused on patients presenting with vestibular symptoms without focal abnormalities on brain magnetic resonance imaging and with interictal epileptic abnormalities on wake or sleep EEG. Results: 31 patients (15 men and 16 women) were included in the study. Visual, auditory, and dysautonomic symptoms were frequently associated with vestibular symptoms. The mean time to diagnosis was 3 years. The duration of attacks was generally short, ranging from a few seconds to a few minutes, with variable frequency. Most patients responded well to antiseizure medication. Some patients showed interictal phenomena, such as permanent instability, raising the possibility of inter/postictal disturbances. Seizures could be triggered by peripheral vestibular stimuli. Interictal EEG abnormalities were observed only during sleep in 25% of patients and predominated in the posterior temporoparietal regions. Discussion: We propose clinical–electro-radiological criteria for defining vestibular epilepsy. These diagnostic criteria overlap with the criteria for vestibular paroxysmia, suggesting the possibility of a single nosological entity.
Commentary
By coincidence, the week before being asked to write this commentary, I saw a 17-year-old boy who recently had his first convulsive seizure that brought his epilepsy to attention. However, since he was 14 years old he had repeated episodes he called “the spinnies,” which had increased in frequency in the previous 12 months. He would feel subjective dizziness, vertigo, and a tilting sensation. This could evolve to reduced hearing and an unpleasant smell and lasted between 30 seconds and 2 minutes. His magnetic resonance imaging (MRI) brain showed a perinatal infarct in the left parietal region. The “spinnies” were clearly focal seizures, but as in many cases, the epilepsy was not recognized until the first tonic–clonic event, being attributed to a variety of non-epileptic vestibular causes. The “spinnies” abated with antiseizure medication.
How can we recognize vestibular epilepsy (VE), and differentiate it from other vestibular pathologies? The differential diagnosis of paroxysmal vestibular symptoms is broad and also includes vestibular neuronitis, benign paroxysmal positional vertigo, vestibular paroxysmia (VP), Meniere's disease, vestibular migraine, episodic ataxia, transient ischaemic attack, multiple sclerosis, functional dizziness, postural orthostatic tachycardia syndrome, and even antiseizure or psychoactive medication toxicity. Vertigo occurs in 5.2% of all adults in 1 year, so is a common consultation in neurology practice. 1 As we will see, as usual, the key is in the history (sometimes supported by EEG).
The authors describe a retrospective single-center cohort of 31 adults from a database of over 2000 patients, expanding on a prior series, who fulfilled the criteria of epileptic seizures with prominent ictal vestibular symptoms, normal MRI brain, and abnormal EEG.2,3 Similar to my patient, many (16 of 31) had been referred to non-neurologists initially, and the average time to diagnosis was 3.1 years, with delays of up to 11 years. Ten of the 31 had isolated vestibular symptoms defined as pure or “idiopathic” VE. The patients tended to be young in age, with an average of 26.5 years. Four patients had more prolonged symptoms of interictal instability or disequilibrium thought to be postictal in origin. Three had “vestibulogenic” seizures triggered by peripheral vestibular stimuli such as head movement.
EEG interictal abnormalities were seen in the right or left posterior temporal or parietal regions (more right than left, 64%), often only during sleep (36%). While the authors do not detail the types of EEG recordings, EEG with sleep, including ambulatory EEG may be needed to detect underlying abnormalities in these patients.
Seventy-four percent of patients were seizure-free or with only limited auras. Three patients (10%) were medication-resistant, while most patients were treatment-responsive.
What are the characteristic features of ictal vestibular symptoms? Ictal symptoms can include sensations of falling, floating, levitation, tilting, sense of imbalance, and rotatory vertigo. The person may not initially mention vertigo so a careful history, delving into any reported “dizziness” to extract the details is essential. In this study, associated symptoms were important in differentiating ictal vestibular seizures from other causes and included auditory symptoms (16%), visual (35%, distorted shapes, and blurred vision), vegetative (vomiting and paleness), or ictal motor signs. Only 2 out of 21 patients had abnormal eye movements (ictal nystagmus and opsoclonus). Falls occurred in this group of patients but are not specific to VE. The presence of other brainstem symptoms and signs should suggest a demyelinating, vascular, or structural cause.
The duration of an event often gives an important clue to etiology—in this study, vestibular seizures lasted from 1 minute to under 1 hour differentiating them from vestibular migraine lasting minutes to hours and VP lasting a shorter period from fractions of a second to several seconds.
The neurological examination including positional maneuvers can help differentiate peripheral from central vertigo and could point away from a central ictal cause. 4 However, the authors noted that mild abnormalities in ENT or tilt table testing including the head impulse test should not exclude VE in the right context.
The authors note the similarity of the clinical presentation and diagnostic criteria to VP, with EEG as the main differentiating factor, and even propose a similar nosological classification. VP is due to compression of the eighth cranial nerve by a vessel or other structural lesion causing transient vestibular symptoms. 5 However, this is akin to comparing trigeminal neuralgia to facial sensory seizures—one is altered peripheral neuronal hyperexcitability, whereas the other is central. Symptoms of VP are confined to the vestibular, sometimes cochlear sphere, but loss of awareness, or other ictal semiology seen in VE are not present. While VP responds to sodium-blocking agents often at low doses, VE responds to a broader range of antiseizure medications. So while VE and VP share characteristics in their respective classifications, a careful history should inform the correct diagnosis.
The authors provide an updated classification of VE—at least 2 recurrent seizures with stereotyped vestibular symptoms, duration 1 minute to <1 hour, absence of MRI abnormalities, and an EEG with tempero-parietal epileptiform abnormalities.
My patient would not qualify for a diagnosis of VE based on these criteria, due to a structural (but epileptogenic lesion) on MRI and an EEG with focal slowing only, despite a clear clinical diagnosis of focal structural epilepsy with prominent vestibular symptoms. The distinction is arbitrary, as a normal MRI and EEG do not preclude a diagnosis of epilepsy, and an “idiopathic” VE is probably just a more localized focal epileptic network involving the primary vestibular cortex.
What is the symptomatogenic zone for ictal vestibular semiology? The authors note that stimulation studies of the vestibular cortex support a perisylvian, parietal operculum or posterior insula origin. Intracranial and functional studies support the retroinsular region incorporating the parieto-insular vestibular cortex and adjacent parieto-temporal junction that process position and head movement as closest to a primary vestibular cortex, although the complexity is beyond the scope of this commentary. Closely linked areas such as the ventral intraparietal area which integrates sensory inputs into visuospatial perception, and the medial superior temporal area which integrates vestibular and visual information, may also produce vestibular symptoms. Proximity to autonomic and auditory cortex, explain semiology evolution.6,7
The authors suggest close collaboration with ENT colleagues and further studies to refine diagnostic criteria. In a patient presenting with paroxysmal vestibular symptoms, we need to carefully consider vestibular seizures in the history, having a lower threshold for obtaining awake and sleep EEG, in order to reduce diagnostic delay. Parietal or posterior cortex epilepsy is one of the most challenging focal epilepsies to localize in the presurgical workup—identifying involvement of the vestibular cortex can be a critical clue to focus accurate intracranial evaluations.
