Epilepsy in spinocerebellar ataxia type 8: a case report

Spinocerebellar ataxia (SCA) is a relatively uncommon condition with a prevalence estimated to be about 2.7 per 1 million population [1]. Clinical features typically include ataxic gait, nystagmus, and cerebellar symptoms such as incoordination. SCA type 8 (SCA8) is among the less commonly seen types of ataxia but is being diagnosed increasingly more often due to increased genetic testing and raised awareness among clinicians. Ataxia, tremor, gait difficulties, nystagmus, and myoclonus are among the commonly seen symptoms in SCA8, but variable manifestations involving cognitive and psychiatric symptoms have been reported, making diagnosis challenging [2, 3]. The patient in this report was diagnosed with SCA8 and had chronic, recurring spells that were confirmed to be epileptic seizures after she was found to have nonconvulsive status epilepticus. Only a single previous case of myoclonic epilepsy was reported in a patient with SCA8 [4]. To the author’s knowledge, the present report describes the first confirmed case of SCA8 with focal onset epilepsy.

A 22-year-old right-handed Caucasian woman with a known diagnosis of SCA8 since the age of 10 years was admitted to our university medical center with encephalopathy and left-sided hemiparesis of unclear cause over the last 3 months. She had been diagnosed with SCA8 at 10 years of age after presenting with ataxia and gait difficulties that progressed rapidly. She was diagnosed at the Children’s Hospital of Nebraska after genetic testing confirmed the diagnosis. She continued to see the geneticists there for management of her condition. Her family was also tested and was found to be negative for genetic mutations, confirming the patient as the only affected family member, probably from a sporadic mutation. Neuropsychological testing was not performed at the time, but the patient’s family reported that she had an average IQ and was able to speak normally and perform daily functions without difficulty.

The patient’s physical examination on admission at our center revealed encephalopathy with left hemiparesis without obvious visual field deficits or other cranial nerve deficits. Magnetic resonance imaging scans revealed leptomeningeal contrast enhancement and edema over the right hemisphere (Fig. 1). The results of lumbar puncture and resulting cerebrospinal fluid studies were unremarkable. A routine electroencephalogram (EEG) revealed independent slowing of both hemispheres, with the right hemisphere showing greater focal slowing and attenuation as well (Fig. 2). Right posterior quadrant epileptiform discharges from an O₂ electrode were occasionally seen in a quasiperiodic manner (Fig. 3). Given these findings, the patient was started on levetiracetam therapy to treat potential epileptogenicity from the right posterior quadrant.

Two days later, she was noted to have frequent spells of confusion and decreased awareness. Owing to concern for ongoing seizures, she was connected to a long-term video EEG monitor for diagnosis. Video recordings captured multiple spells, each lasting 2–3 minutes, of loss of awareness with left gaze deviation and oromanual automatisms and staring with postictal lethargy and confusion consistent with clinical seizures. EEG captured posterior quadrant onset from both left and right hemispheres consistent with electroclinical seizures. A clear lateralization of onset was not seen with many of these seizures, owing to rapid bilateral involvement of both posterior quadrants (Figs. 4, 5, and 6). Many of these seizures occurred frequently over a 2–3-hour period, meeting criteria for status epilepticus. She was started on lacosamide therapy, and her dose of levetiracetam was increased. Her seizures resolved within a few hours of increasing her antiepileptic therapy.

Her family revealed that she had been having similar spells since the age of 12 years and that they had witnessed at least 15–20 similar spells in the past that were not previously recognized as seizures. Many of these spells were associated with nausea and vomiting, findings that were not captured on our video EEG recordings.

She continued to show improvement in mental status, and her left hemiparesis showed progressive improvement over the next few days with antiepileptic therapy and physical therapy. She was discharged to a rehabilitation facility on lacosamide and levetiracetam, continues to return for follow-up as an outpatient, and is currently doing well without any further seizures. When she was seen 3 months after her admission, her left hemiparesis had improved, and she had returned to her previous mental baseline.

SCA8 is a neurodegenerative disease inherited in an autosomal dominant pattern and should be considered in the differential diagnosis of progressive ataxias. SCA8 is distinct in several aspects from other genetic progressive ataxias [5]. Most notably, the symptomatology of SCA8 is remarkably variable and at times episodic [3, 6].

Gait difficulty, ataxia, dysarthria, dysphagia, sensorimotor manifestations, nystagmus, and cognitive difficulties are reported in many patients with this condition [3, 7]. There is a single prior case report of epilepsy in a patient with SCA8, but that patient was reported to have myoclonic epilepsy, in contrast to our patient, who presented with focal epilepsy of posterior quadrant onset [4]. Seizure-like episodes in SCA8 have also been reported before, but these have been EEG-negative and suggestive of dystonic episodes or other movement disorders, such as chorea, rather than true epileptic seizures [8, 9].

Seizures are a known feature of SCA10 and SCA13 but have been reported only once before in SCA8 [10, 11]. The only other case of epilepsy in SCA8 was of the myoclonic epilepsy subtype. Our patient has focal epilepsy of posterior quadrant onset, which makes her presentation a unique phenotype of SCA8. We hypothesize that her SCA8 is probably causative of her epilepsy rather than a coincidental finding, because she has an unusual semiology for her seizures in addition to other features of SCA8, which suggest association by causation rather than coincidence. Moreover, it is highly unlikely that she would have an uncommon occipital seizure onset as a coincidental finding with her rare genetic condition, rather than having the occipital epilepsy as a part of its phenotype. Pure occipital onset epilepsy is relatively uncommon, and for it to occur concurrently in a patient with a rare genetic syndrome suggests genetic causation of this occipital epilepsy rather than coincidence. The patient has no family history of epilepsy, and no other family members have SCA8. Our patient does have presenting ataxia, which resulted in her initial diagnosis based on genetic testing. She also had multiple witnessed spells during her lifetime since the age of 12 years, which were retrospectively recognized as seizures. Her semiology of staring, loss of awareness, and automatisms with nausea and vomiting is consistent with posterior quadrant and occipital involvement in her seizures. The author hypothesizes that she may have had multiple unrecognized seizures within a few hours to days resulting in her left hemiparesis and necessitating hospital admission. The presence of right hemispheric meningeal enhancement, right hemispheric attenuation on EEG, right posterior quadrant discharges on interictal EEG, and bilateral posterior quadrant involvement with her seizures and improvement in hemiparesis following antiepileptic therapy help to support this hypothesis.

Levetiracetam and lacosamide were chosen for their ease of administration during status epilepticus and continued use on an outpatient basis. The patient in the present case does not have myoclonus, which is a known feature of SCA8, but levetiracetam was chosen to help with potential myoclonus as well [3]. Psychiatric symptoms have also been reported in patients with SCA8, but the present patient did not have any such complaints, which made the author feel more comfortable in choosing levetiracetam for her seizure therapy [3].

SCA8 is an uncommon type of SCA and can have a highly variable presentation (Table 1). Seizures are known to occur in the SCAs and must always be kept in mind as a possibility, especially due to the presence of a known neurodegenerative/genetic disease. Spells of altered awareness with or without automatisms are highly concerning for epileptic events, but nonepileptic causes such as movement disorders and psychogenic spells must always be kept in the differential diagnosis. Video EEG monitoring is essential for capturing these spells to confirm or exclude epileptic etiology and must be used accordingly. Antiepileptic therapy must be instituted when needed in such patients, and the choice of agent is determined by the ease of administration and comorbidities associated with them. Expert evaluation is highly recommended when treating such patients, and multidisciplinary collaboration for management involving epileptologists, movement disorder specialists, psychiatrists, physical medicine doctors, and others is highly advised. Genetic testing helps to confirm the diagnosis and establish care with appropriate specialists.