Ictal apnea: A prospective monocentric study in patients with epilepsy

Abstract

Background and purpose: Ictal respiratory disturbances have increasingly been reported, in both generalized and focal seizures, especially involving the temporal lobe. Recognition of ictal breathing impairment has gained importance for the risk of sudden unexpected death in epilepsy (SUDEP). The aim of this study was to evaluate the incidence of ictal apnea (IA) and related hypoxemia during seizures.

Methods: We collected and analyzed electroclinical data from consecutive patients undergoing long-term video-electroencephalographic (video-EEG) monitoring with cardiorespiratory polygraphy. Patients were recruited at the epilepsy monitoring unit of the Civil Hospital of Baggiovara, Modena Academic Hospital, from April 2020 to February 2022.

Results: A total of 552 seizures were recorded in 63 patients. IA was observed in 57 of 552 (10.3%) seizures in 16 of 63 (25.4%) patients. Thirteen (81.2%) patients had focal seizures, and 11 of 16 patients showing IA had a diagnosis of temporal lobe epilepsy; two had a diagnosis of frontal lobe epilepsy and three of epileptic encephalopathy. Apnea agnosia was reported in all seizure types. Hypoxemia was observed in 25 of 57 (43.9%) seizures with IA, and the severity of hypoxemia was related to apnea duration. Apnea duration was significantly associated with epilepsy of unknown etiology (magnetic resonance imaging negative) and with older age at epilepsy onset (p < 0.001).

Conclusions: Ictal respiratory changes are a frequent clinical phenomenon, more likely to occur in focal epilepsies, although detected even in patients with epileptic encephalopathy. Our findings emphasize the need for respiratory polygraphy during long-term video-EEG monitoring for diagnostic and prognostic purposes, as well as in relation to the potential link of ictal apnea with the SUDEP risk.

Keywords: central apnea; electroencephalography; hypoxia; sudden unexpected death in epilepsy; temporal lobe epilepsy.

FIGURE 1

(a) A 20‐year‐old male with ictal apnea seizures. On the left, a coronal T2 fluid‐attenuated inversion recovery magnetic resonance imaging scan shows the presence of a left temporopolar encephalocele (red arrow). On the right, the electroencephalogram (EEG; 120 s) shows a left temporal seizure arising from the frontotemporal channels (Fp1‐F7, F7‐T3), rapidly involving the ipsilateral and contralateral frontal regions including the anterior vertex. The ictal discharge (indicated by the purple arrow) is characterized by low‐voltage fast rhythms evolving in sharply contoured theta and then delta rhythmic activity with diffuse abrupt termination. Ictal apnea starts during the ictal phase in association with bradycardia. Ictal apnea duration is indicated by the black bar. Red channel: electrocardiogram; blue channel: thoracoabdominal respirogram. (b) A 14‐year‐old male patient with Lennox–Gastaut epileptic encephalopathy. During non‐rapid eye movement sleep, the EEG shows abrupt diffuse fast activity (as indicated by the purple arrow) predominant over the frontocentral and vertex regions for 20 s, followed by slow activity. The polygraphy shows ictal tachycardia (red channel) and flattening of the thoracoabdominal respirogram (light blue channel; indicated by the black bar). No significant muscle activity was recorded (mylohyoid and left and right tibialis anterior muscles) during the epileptic discharge [Colour figure can be viewed at wileyonlinelibrary.com

FIGURE 2

Longer ictal apnea (IA) duration is significantly associated with clinical variables. Box‐and‐whisker plots show the association between the IA duration and (a) seizures with focal onset (p < 0.001), (b) epilepsy with unknown etiology (p < 0.05), and (c) older age of epilepsy onset (R = 0.591, p < 0.001). The central horizontal line of the boxes marks the median of the sample, and the “x” in the middle of each box represents the mean of the sample. The upper and lower edges of the box (the hinges) mark the 25th and 75th percentiles (the central 50% of values fall within the box). Finally, the open circles represent individual patients. Longer IA duration was significantly associated with seizures with focal onset (p < 0.001; a), epilepsy of unknown etiology (p < 0.05; b), and older age of epilepsy onset (R = 0.591, p < 0.001; c)

FIGURE 3

The length of ictal apnea (IA) was inversely associated with hypoxemia nadir (R = −0.620, p < 0.001)