The Electrophysiological Findings in Spinocerebellar Ataxia Type 6: Evidence From 24 Patients

PURPOSE

Peripheral neuropathy has been reported commonly in several spinocerebellar ataxia (SCA) types. To date, there is a lack of robust evidence for neuropathy or neuronopathy in SCA type 6 (SCA6). Here, we aim to evaluate the presence of neuropathy or neuronopathy in a cohort of SCA6 patients.

METHODS

Twenty-four individuals with genetically confirmed SCA6 underwent detailed neurophysiological assessment. This included nerve conduction studies, and in some, cutaneous silent periods, blink reflexes, tilt table tests, quantitative sudomotor axon reflex tests, and somatosensory (median and tibial) evoked potentials.

RESULTS

Mean age was 56.1 years (range, 22-94 years) at the time of testing. Four patients were presymptomatic of SCA6 at recruitment. The mean disease duration of symptomatic patients was 11.9 years (range, 1-40 years). Most patients (79.2%, 19/24) had no neurophysiological evidence of a peripheral neuropathy. One with impaired glucose tolerance had mild, large, and small fiber sensorimotor polyneuropathy. One elderly patient had length-dependent axonal sensorimotor polyneuropathy. Two had minor sensory abnormalities (one had type II diabetes and previous chemotherapy). One other had minor small fiber abnormalities. Ten patients (41.7%) had median neuropathies at the wrist. All somatosensory evoked potential (15/15), and most autonomic function tests (13/14) were normal.

CONCLUSIONS

A large proportion of subjects (79.2%) in our cohort had no evidence of large or small fiber neuropathy. This study does not support the presence of neuropathy or neuronopathy as a common finding in SCA6 and confirms the importance of considering comorbidities as the cause of neurophysiological abnormalities.

Overview of the Clinical Approach to Individuals With Cerebellar Ataxia and Neuropathy

Increasingly, cerebellar syndromes are recognized as affecting multiple systems. Extracerebellar features include peripheral neuropathies affecting proprioception; cranial neuropathies such as auditory and vestibular; and neuronopathies, for example, dorsal root and vestibular. The presence of such features, which in and of themselves may cause ataxia, likely contribute to key disabilities such as gait instability and falls. Based on the evolving available literature and experience, we outline a clinical approach to the diagnosis of adult-onset ataxia where a combination of cerebellar and peripheral or cranial nerve pathology exists. Objective diagnostic modalities including electrophysiology, oculomotor, and vestibular function testing are invaluable in accurately defining an individual's phenotype. Advances in MRI techniques have led to an increased recognition of disease-specific patterns of cerebellar pathology, including those conditions where neuronopathies may be involved. Depending on availability, a stepwise approach to genetic testing is suggested. This is guided by factors such as pattern of inheritance and age at disease onset, and genetic testing may range from specific genetic panels through to whole-exome and whole-genome sequencing. Management is best performed with the involvement of a multidisciplinary team, aiming at minimization of complications such as falls and aspiration pneumonia and maximizing functional status.

Long-term mood, quality of life, and seizure freedom in intracranial EEG epilepsy surgery

OBJECTIVES

To determine the long-term outcomes in patients undergoing intracranial EEG (iEEG) evaluation for epilepsy surgery in terms of seizure freedom, mood, and quality of life at St. Vincent's Hospital, Melbourne.

METHODS

Patients who underwent iEEG between 1999 and 2016 were identified. Patients were retrospectively assessed between 2014 and 2017 by specialist clinic record review and telephone survey with standardized validated questionnaires for: 1) seizure freedom using the Engel classification; 2) Mood using the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E); 3) Quality-of-life outcomes using the QOLIE-10 questionnaire. Summary statistics and univariate analysis were performed to investigate variables for significance.

RESULTS

Seventy one patients underwent iEEG surgery: 49 Subdural, 14 Depths, 8 Combination with 62/68 (91.9%) of those still alive, available at last follow-up by telephone survey or medical record review (median of 8.2 years). The estimated epileptogenic zone was 62% temporal and 38% extra-temporal. At last follow-up, 69.4% (43/62) were Engel Class I and 30.6% (19/62) were Engel Class II-IV. Further, a depressive episode (NDDI-E > 15)was observed in 34% (16/47), while a 'better quality of life' (QOLIE-10 score < 25) was noted in 74% (31/42). Quality of life (p < 0.001) but not mood (p = 0.24) was associated with seizure freedom.

SIGNIFICANCE

Long-term seizure freedom can be observed in patients undergoing complex epilepsy surgery with iEEG evaluation and is associated with good quality of life.

Seizure Forecasting Using a Novel Sub-Scalp Ultra-Long Term EEG Monitoring System

Accurate identification of seizure activity, both clinical and subclinical, has important implications in the management of epilepsy. Accurate recognition of seizure activity is essential for diagnostic, management and forecasting purposes, but patient-reported seizures have been shown to be unreliable. Earlier work has revealed accurate capture of electrographic seizures and forecasting is possible with an implantable intracranial device, but less invasive electroencephalography (EEG) recording systems would be optimal. Here, we present preliminary results of seizure detection and forecasting with a minimally invasive sub-scalp device that continuously records EEG. Five participants with refractory epilepsy who experience at least two clinically identifiable seizures monthly have been implanted with sub-scalp devices (Minder®), providing two channels of data from both hemispheres of the brain. Data is continuously captured via a behind-the-ear system, which also powers the device, and transferred wirelessly to a mobile phone, from where it is accessible remotely via cloud storage. EEG recordings from the sub-scalp device were compared to data recorded from a conventional system during a 1-week ambulatory video-EEG monitoring session. Suspect epileptiform activity (EA) was detected using machine learning algorithms and reviewed by trained neurophysiologists. Seizure forecasting was demonstrated retrospectively by utilizing cycles in EA and previous seizure times. The procedures and devices were well-tolerated and no significant complications have been reported. Seizures were accurately identified on the sub-scalp system, as visually confirmed by periods of concurrent conventional scalp EEG recordings. The data acquired also allowed seizure forecasting to be successfully undertaken. The area under the receiver operating characteristic curve (AUC score) achieved (0.88), which is comparable to the best score in recent, state-of-the-art forecasting work using intracranial EEG.

Combining cutaneous silent periods with quantitative sudomotor axon reflex testing in the assessment of diabetic small fiber neuropathy

OBJECTIVE

Routine electrophysiological testing is often normal in the evaluation of painful diabetic neuropathy, as it is unable to detect dysfunction of thinly myelinated (Aδ) and unmyelinated (C) small fibers. Although cutaneous silent periods (CSP) and quantitative sudomotor axon reflex testing (QSART) respectively evaluate these fiber types in the extremities, these two tests have yet to be assessed together.

METHODS

26 patients with a clinical diagnosis of small fiber neuropathy (SFN) and 26 age-matched controls were assessed. Nine patients had Type I diabetes, nine had Type II diabetes, and eight had impaired glucose tolerance. The CSP onset latency and duration were recorded in each extremity. QSART was performed on the right side.

RESULTS

58% (15/26) of patients had abnormal sweat volumes obtained from QSART, while 50% (13/26) of patients had abnormal CSP responses. Combining these two tests increased the sensitivity of testing to 77% (20/26). Abnormalities were seen equally across all patient groups.

CONCLUSIONS

Combining CSP with QSART significantly increases the sensitivity of testing when assessing patients with SFN related to diabetes, or prediabetes.

SIGNIFICANCE

For clinically suspected SFN, it is preferable to test more than one small fiber type, as each possess different structural and functional properties and may be heterogeneously affected between patients.