Why do patients experience vomiting during seizures, and is it a common occurrence?

Vomiting During Seizures: Mechanism and Frequency

Vomiting during seizures occurs due to ictal activation of temporal lobe structures (particularly the mesial temporal regions and amygdala) that trigger brainstem vomiting centers, and while not extremely common, it represents a recognized autonomic manifestation of partial seizures, particularly those of temporal lobe origin. 1

Why Vomiting Occurs During Seizures

Neuroanatomical Basis

• Ictal discharges originating in the mesial temporal structures (especially the amygdala) can trigger vomiting without requiring spread to the insular cortex, as demonstrated by stereo-EEG studies showing vomiting limited to anterior temporal structure activation alone. 2
• The seizure discharge activates the central autonomic network, which includes subcortical structures such as the dorsal vagal complex and central pattern generators (CPG) located in the reticular area of the brainstem. 2
• Vomiting represents an autonomic symptom mediated by activation of the central autonomic network rather than a simple reaction to motor manifestations of the seizure. 3

Seizure Types Associated with Vomiting

• Vomiting can occur in both simple partial seizures (without loss of consciousness) and complex partial seizures (with impaired awareness), with temporal lobe origin being the most common source. 2, 4, 5
• Parietal lobe involvement has also been documented in cases where vomiting was the sole symptom of simple partial seizures. 4
• The ictal discharge may remain localized to temporal structures or spread to involve both mesial and lateral temporal regions at the time of vomiting. 2

How Common Is Ictal Vomiting?

Frequency and Clinical Context

• Ictal vomiting is considered an uncommon manifestation of epilepsy, with only 44 cases of nonidiopathic focal epilepsy with seizure-associated vomiting reported in the literature as of 2015. 2
• Autonomic symptoms like vomiting frequently occur during epileptic seizures but typically as an accompaniment to other seizure symptoms rather than as the predominant manifestation. 3
• When vomiting does occur, it typically appears early in the course of the seizure when rhythmic discharges involve the temporal regions. 5

Clinical Significance and Management

• The 2024 American Heart Association guidelines specifically recommend placing seizure patients on their side in the recovery position to reduce aspiration risk if vomiting occurs during the seizure or postictal period, acknowledging vomiting as a recognized complication. 1, 6
• Vomiting can occur during the ictal period (during the seizure) or the postictal period (after the seizure ends), necessitating protective positioning throughout both phases. 1

Important Clinical Pitfalls

Differential Diagnosis Challenges

• When autonomic symptoms like vomiting represent the sole seizure manifestation, they can pose significant diagnostic problems and be confused with various non-epileptic gastrointestinal conditions. 3
• Scalp EEG may show no electrical modification during vomiting episodes, requiring more invasive monitoring (stereo-EEG or subdural grids) for definitive diagnosis. 2
• The stereotypical and paroxysmal nature of episodes, along with response to antiepileptic medication, helps distinguish ictal vomiting from other causes. 4

Lateralization Considerations

• Ictal vomiting and retching may indicate seizure onset in the non-dominant hemisphere, though this is not absolute. 3
• Some studies suggest ictal vomiting does not reliably lateralize temporal lobe epilepsy and is not specific to particular pathology. 5