If the mother becomes symptomatic, it is usually in the third trimester. Symptoms include fever, myalgias, arthralgias and headache. Miscarriage, stillbirth and preterm labor are complications of this infection. Symptoms last 7–10 days. Neonatal infection (granulomatosis infantiseptica): There are two forms. One, an early-onset sepsis, with Listeria acquired in utero, results in premature birth. Listeria can be isolated in the placenta, blood, meconium, nose, ears, and throat. Another, late-onset meningitis is acquired through vaginal transmission, although it also has been reported with caesarean deliveries. Central nervous system (CNS) infection: Listeria has a predilection for the brain parenchyma, especially the brain stem, and the meninges. It can cause cranial nerve palsies, encephalitis, meningitis, meningoencephalitis and abscesses. Mental status changes are common. Seizures occur in at least 25% of patients. Gastroenteritis: L. monocytogenes can produce food-borne diarrheal disease, which typically is noninvasive. The median incubation period is 21 days, with diarrhea lasting anywhere from 1–3 days. Affected people present with fever, muscle aches, gastrointestinal nausea or diarrhea, headache, stiff neck, confusion, loss of balance, or convulsions.Listeria has also been reported to colonize the hearts of some patients. The overall incidence of cardiac infections caused by Listeria is relatively low, with 7–10% of case reports indicating some form of heart involvement.
In these cases it is usually the medial pterygoid or the buccinator muscles. Oral surgery procedures, as in the extraction of lower molar teeth, may cause trismus as a result either of inflammation to the muscles of mastication or direct trauma to the TMJ. Barbing of needles at the time of injection followed by tissue damage on withdrawal of the barbed needle causes post-injection persistent paresthesia, trismus and paresis. Treatment: in acute phase:
Heat therapy
Analgesics
A soft diet
Muscle relaxants (if necessary)
Note: When acute phase is over the patient should be advised to initiate physiotherapy for opening and closing mouth. Trauma
Fractures, particularly those of the mandible and fractures of zygomatic arch and zygomatic arch complex, accidental incorporation of foreign bodies due to external traumatic injury. Treatment: fracture reduction, removal of foreign bodies with antibiotic coverage

TMJ disorders
Extra-capsular disorders – Myofascial pain dysfunction syndrome
Intra-capsular problems – Disc displacement, arthritis, fibrosis,  etc. Acute closed locked conditions – displaced meniscus

Tumors and oral care
Rarely, trismus is a symptom of nasopharyngeal or infratemporal tumors/ fibrosis of temporalis tendon, when patient has limited mouth opening, always premalignant conditions like oral submucous fibrosis (OSMF) should also be considered in differential diagnosis. Drug therapy
Succinyl choline, phenothiazines and tricyclic antidepressants causes trismus as a secondary effect. Trismus can be seen as an extra-pyramidal side-effect of metoclopromide, phenothiazines and other medications. Radiotherapy and chemotherapy
Complications of radiotherapy:
Osteoradionecrosis may result in pain, trismus, suppuration and occasionally a foul smelling wound. When muscles of mastication are within the field of radiation, it leads to fibrosis and result in decreased mouth opening.