Epileptic aura continua: a case report with response to brivaracetam

Dear Editor:

In the broadest sense of the term, epilepsia partialis continua (EPC) is a form of focal status epilepticus associated with continuous motor, somatosensory, visual, olfactory, auditory, or cognitive symptoms, but preserved awareness, lasting ≥ 1 hour, and caused by locally restricted epileptiform activity.¹ Some authors use the term “aura continua” to refer to the non-motor form of EPC.^1–3 According to the International League Against Epilepsy’s latest classification of status epilepticus, EPC is the motor form and aura continua belongs to the group of focal non-convulsive status epilepticus without impairment of consciousness.⁴ No demographic data are available for aura continua; however, EPC is known to be a rare entity, with estimated prevalence of less than 1 case per million population.⁵ EPC may be classified into 4 categories, according to disease progression: isolated episode, chronic repetitive non-progressive, chronic persistent non-progressive, and chronic progressive. It may be caused by a wide range of factors, including inflammation, infection, neurovascular processes, tumours, trauma, mitochondrial dysfunction, and metabolic disorders.^1,2 Treatment of this condition is highly challenging; furthermore, little evidence is available on the most appropriate drug due to its low prevalence. We present the case of a patient with somatosensory aura continua in the context of drug-resistant post-traumatic structural epilepsy.

Our patient was a 35-year-old right-handed man with history of head trauma at the age of 22 years, with right parietal haemorrhagic contusion secondary to the depressed skull fracture; he underwent surgery to remove bone fragments from the brain parenchyma. The neurological examination performed after the head trauma revealed right hemiparesis (4/5 strength on the Medical Research Council scale), right hemihypoaesthesia, and mild executive, visuomotor, and visuoconstruction impairment, which resolved completely over the following 6 months. He also presented focal motor seizures with preserved awareness, which were treated with phenytoin. Two months later, he began to present somatosensory symptoms in the form of paraesthesia, starting on the left side of the face and progressing to brachiocrural paraesthesia, followed by clonic movements in the left arm. Treatment was started with valproic acid. After 3 years of seizure freedom, the drug was progressively withdrawn, but the patient presented stereotyped, paroxysmal episodes consisting of fluctuating paraesthesia starting in the left thoracic region and progressing to the ipsilateral distal crural area and subsequently to the knee; episodes lasted between 1 and 5 hours and presented at a frequency of 10 episodes per month, usually in clusters. These findings suggest chronic repetitive non-progressive aura continua type 2a of structural aetiology,² originating in the right parietal lobe, or central neuropathic pain. Gabapentin achieved no improvement. Two interictal serial electroencephalography (EEG) studies did not detect epileptiform activity. Levetiracetam, valproic acid, and oxcarbazepine at optimal doses achieved no improvement. The patient presented adverse reactions to topiramate. Seizure frequency did not change at any point during the process, with 10 years of follow-up. Brivaracetam achieved a satisfactory response; the patient has remained seizure-free for 3 months, for the first time in 10 years of follow-up.

We present a case of aura continua, which is an infrequent entity with very few reported cases, especially in the case of the sensory type, making the condition a true diagnostic and therapeutic challenge.¹ While interictal EEG alterations are frequent, a lack of epileptiform activity does not rule out diagnosis.² In our patient, the stereotyped, paroxysmal nature of the seizures and their correlation with the traumatic brain injury enabled us to establish the diagnosis. The combination of hyperexcitability in a well-delimited focal area and preservation of mechanisms of lateral inhibition allows for the appearance of this epileptic phenomenon with limited propagation.^2,3 Treatment focuses on managing the underlying cause.⁶ Little evidence is available on the efficacy of antiepileptic drugs, with topiramate and levetiracetam showing the best results.^1–3 Brivaracetam is a selective high-affinity synaptic vesicle protein 2A (SV2A) ligand; it shows 15 to 30 times higher affinity for SV2A than levetiracetam.⁷ Furthermore, brivaracetam does not modulate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors,⁸ whereas levetiracetam does; this suggests that both drugs have different pharmacological profiles. Brivaracetam has been approved in the United States⁹ and the European Union¹⁰ as a complementary treatment for focal seizures with or without secondary generalisation in patients aged 16 years and older. This is the first reported case of aura continua showing fast response to brivaracetam, and suggests that the drug may be a treatment option for these patients. However, further evidence is needed to make recommendations.

Our study was approved by the clinical research ethics committee at Hospital del Mar, Barcelona (Spain).

Funding

This study has received no funding from any public, private, or non-profit organisation.

Conflicts of interest

The authors have no conflicts of interest to declare.