Prolonged Seizures and Trismus (Lockjaw)
Prolonged seizures do not directly cause trismus (lockjaw), but the intense muscle contractions during seizure activity can result in jaw muscle spasm and temporary difficulty opening the mouth during the ictal and immediate postictal period.
Understanding the Relationship
The connection between seizures and jaw involvement relates to the tonic-clonic muscle activity during seizure episodes, not a direct causative mechanism for true trismus:
During Active Seizure Activity
- Seizures involve erratic movements of the head, body, and extremities that can result in significant traumatic injury, including jaw clenching during the tonic phase 1
- The masseter muscles undergo intense contraction during generalized tonic-clonic seizures, which can create temporary jaw rigidity 1
- Prolonged seizures (lasting >180 seconds) are associated with greater postictal confusion and inadequate oxygenation resulting in increased hypoxia-related risks, but lockjaw is not listed among the documented complications 1
True Trismus vs. Seizure-Related Jaw Clenching
Trismus is defined as a prolonged, tetanic spasm of the jaw muscles by which normal opening of the mouth is restricted, and has distinct etiologies separate from seizure activity 2:
- Trismus results from dental abscess, trauma, radiation, infection, inflammatory diseases, temporomandibular disorders, or malignancy 2, 3
- Masseter spasticity requiring treatment is a separate neurological condition from seizure-related muscle contractions 4
- Trismus from leukemic cell infiltration into facial muscles represents a pathological process distinct from seizure activity 5
Clinical Implications
What Actually Happens During Prolonged Seizures
Prolonged seizures produce cerebral and cardiovascular complications from hypoxia, not sustained jaw muscle dysfunction 1:
- In animal studies, seizures exceeding 30 minutes produce structural brain damage and cardiovascular complications 1
- Postictal confusion and amnesia are the primary neurological sequelae 1
- Nothing should be put in the mouth during a seizure, as this creates injury risk without preventing any actual complication 1
Post-Seizure Management Priorities
First aid providers should place the person on their side in the recovery position and clear the area around them to minimize injury risk 1:
- Activate EMS for seizures lasting >5 minutes, as these may not stop spontaneously and require anticonvulsant medications 1
- The person should not be restrained during seizure activity 1
- Stay with the person and monitor for return to baseline within 5-10 minutes after seizure cessation 1
Critical Pitfall
If a patient presents with persistent trismus following a seizure, do not attribute the jaw restriction solely to the seizure without investigating alternative causes 2, 3. True trismus persisting beyond the immediate postictal period warrants evaluation for:
- Temporomandibular joint injury from seizure-related trauma 3
- Underlying infection or inflammatory process 2, 6
- Malignancy, particularly if accompanied by other concerning features 5, 3
The jaw clenching during a seizure is a transient phenomenon of the ictal event itself, not a complication that persists as true trismus requiring specific intervention beyond standard seizure management.