Quantitative and qualitative analysis of ictal vocalization in focal epilepsy syndromes
Introduction from Dr Markus Reuber, editor-in-chief of Seizure
Neurophysiologically, vision is the dominant sense for humans. A much larger proportion of our cerebral cortex is devoted to vision, than touch, hearing or our other senses. The visual cortex is the part of the brain which lights up most brightly on Positron Emission Tomography (PET) images of the human brain. Not surprisingly, visible information is also predominant in medicine – including the assessment and differentiation of seizures. Especially since video-EEG examinations have become more accessible (and since home video recording devices are almost universally available) epileptologists have increasingly based their diagnosis on things they can see – either in terms of clinical manifestations, in the EEG or on brain imaging. My editor’s choice by Hartl et al. from the current issue of Seizure focuses specifically on audible ictal features but reminds us that an optimal diagnostic process calls on all of our senses (1).
Previous studies have described the wide range of audible pointers allowing clinicians to distinguish between epilepsy and other attack disorders when they hear patients’ descriptions of their attacks in outpatient conversations (2). Audible features can also help distinguish between epilepsy and nonepileptic seizures (NES) when sound recordings of seizures are available: bilateral tonic clonic seizures (BTCS) often involve a prolonged, laryngeal, high-pitched expiratory vocalisation during the tonic phase or more guttural noises during the clonic phase. In one study the laryngeal sound differentiated BTCS from NES with a sensitivity of 85% and a specificity of 100% (3). Similarly stertorous (snoring-like) breathing in the postictal phase was identified as a potential audible characteristic of differential diagnostic value – found to be present in 91% of BTCS and no convulsive NES (4).
My editor’s choice examines ictal vocalisations more closely and focuses on their localising value in patients with epilepsy. Ictal vocalisation was observed in nearly 40% of seizures. Although the phenomenon occurred with similar frequency in patients with temporal and frontal lobe epilepsies, the co-occurrence of vocalisation and ictal automatisms identified patients with temporal seizure onset with a sensitivity of 92% and specificity of 70%. Quantitative analysis of vocalisation intensity provided more information of localizing value: Frontal lobe seizures were characterised by a greater intensity range, intensity variation and intensity increase at the beginning of the vocalization.
Epileptologists do not just need to keep their eyes open: they need to stop, look & LISTEN.
1) Hartl E, Knoche T, Choupina H, Rémi J, Vollmar C, Cunha J.P.S, Noachtar S. Quantitative and qualitative analysis of ictal vocalization in focal epilepsy syndromes. Seizure 2018
2) Reuber M, Monzoni C, Sharrack B, Plug L. Using Conversation Analysis to distinguish between epilepsy and non-epileptic seizures: a prospective blinded multirater study. Epilepsy and Behavior 2009;16: 139-44.
3) Millichap JG. Diagnostic utility of the ictal cry. Pediatric Neurology Briefs 2010;24:63-64.
4) Sen A. Stertorous breathing is a reliably identified sign that helps in the differentiation of epileptic from psychogenic Nonepileptic convulsions: an audit. Epilepsy Research 2007;77:62-64.