Insular Epilepsy: The Great Mimic

Focal epilepsy

Insular epilepsy is easy to miss because seizures arising in the insula can imitate temporal, frontal or parietal seizures and may spread rapidly into those networks before the most obvious signs appear.

Central point: A throat-tightening sensation, painful or thermal sensory symptoms, or unusual autonomic symptoms can suggest insular involvement — but no single symptom proves the seizure starts in the insula.

Why the insula is difficult to recognise

The insula lies deep within the lateral sulcus and has dense connections with frontal, temporal, parietal, limbic and autonomic networks. Seizures can therefore begin with subtle internal sensations and then spread quickly, producing more familiar temporal or frontal-looking behaviour.

Cervico-laryngeal and breathing sensations

One of the more characteristic insular patterns is cervico-laryngeal discomfort: throat tightness, a sensation of choking or strangulation, laryngeal constriction, unpleasant chest or throat sensations, or subjective breathlessness. These symptoms can be frightening and may be mistaken for panic, reflux or respiratory disease.

Painful, thermal and widespread sensory symptoms

Insular seizures can produce paraesthesia affecting a large or bilateral body area and can be perceived as hot, cold or painful. Pain as an ictal symptom is uncommon overall, but when brief, stereotyped and recurrent it can be an important clue in specialist assessment.

Other possible symptoms

Reported features include hypersalivation, nausea or epigastric discomfort, gustatory sensations, auditory phenomena, vestibular symptoms, speech disturbance and autonomic changes. Because these features also occur in other focal epilepsies, the sequence and combination matter more than any single symptom.

Why it can look frontal or temporal

Rapid spread from the insula can produce hypermotor activity, tonic posturing, automatisms or impaired responsiveness. Recent systematic review work has reinforced that hyperkinetic seizures can arise from insular and insulo-opercular networks, which is one reason the older assumption that dramatic sleep-related motor seizures must be frontal is too simplistic.

Why scalp EEG may mislead

The insula is deep and partly covered by the opercula, so scalp EEG may fail to show the true onset or may suggest activity over nearby temporal or frontal regions after propagation. When insular epilepsy is strongly suspected and surgery is being considered, stereo-EEG may be needed to test the hypothesis directly.

Causes and imaging

Reported causes include focal cortical dysplasia, tumours, vascular lesions and other focal structural abnormalities. MRI can be normal, and even when a lesion is visible, electroclinical correlation is needed to establish whether it is the epileptogenic source.

Treatment

Treatment begins with antiseizure medication for focal epilepsy. Drug-resistant insular epilepsy should be assessed in a tertiary epilepsy centre. Surgery can be technically challenging because the insula is deep and close to important vascular and functional structures, so presurgical localisation and risk assessment are especially important.

Autonomic Seizures · Breathing and Seizures · Frontal Lobe Epilepsy · Temporal Lobe Epilepsy · Epilepsy Surgery and Presurgical Assessment