The incidence of tetanus is estimated to be between 500,000 to one million cases per year worldwide. Lack of immunization is the greatest risk factor for contracting tetanus, resulting in a more frequent incidence of tetanus in the elderly in developed countries, and is associated with a mortality rate of 10%–40%. Modern intensive care management focuses on preventing death from acute respiratory failure (1).
Trismus, i.e., increased masseter tone, is the initial symptom in 50%–75% of cases of tetanus (2). There may also be frequent muscular spasms of varying severity (3). We report a case in which mandibular nerve blocks were used to obtain masseter relaxation, to facilitate removal of dentures in a patient in whom the spasms caused painful biting of the tongue.
An 80-yr-old woman sustained a pretibial laceration while in her garden. Her wound was cleaned and closed with 50 sutures. Her last antitetanus vaccine had been given more than 30 yr previously. She received an antitetanus vaccine at the emergency department. Although recommended by French guidelines, no immunoglobulin was administered. Five days later, she was admitted for débridement, excision, and antibiotic treatment of a necrotic and malodorous wound. On the eighth day, she developed trismus and nuchal rigidity and was transferred to the intensive care unit. Orofacial causes and dystonic drug reactions were excluded. Human tetanus immunoglobulin 3500 IU (Gammatetanos®, LFB) was given IM. Despite the avoidance of unnecessary stimulation, she developed severe and painful masseter spasms, during which she violently bit the tip of her tongue with her dentures. The dentures could not be removed because the mouth could not be opened more than 3 mm (Fig. 1A).
Bilateral mandibular nerve blocks were performed via a lateral extraoral approach. With the patient conscious and cooperative in the sitting position, a 50-mm needle (Polymedic™) was inserted below the midpoint of the zygomatic arch. The needle was then advanced perpendicularly to the face and withdrawn and redirected slightly posteriorly to reach behind the posterior border of the pterygoid plate. The patient did not report any paresthesias. After a negative aspiration, 5 mL mepivacaine 2% was injected on each side. After 20 min, the masseter muscles were sufficiently relaxed to allow the mouth to be opened 25 mm, and the dentures were removed. Mouth care was given with tooth cleaning and swabbing the oropharynx with an applicator with povidone iodine (Fig. 1B). The motor block persisted for 2 h; no side effects (including intradural and/or vascular injection, facial palsy, strabismus, diplopia, ptosis ophthalmoplegia, or temporary blindness) were noted. No additional episodes of tongue biting occurred and the spasms became less painful.
There was no generalized tetanus at any time. The patient was managed in the intensive care unit for 14 days. She did not have any difficulty with swallowing at any time. Enteral nutrition was given via a nasogastric tube. The trismus decreased on day 24; normal mouth opening returned after 6 wk. She fully recovered at 10 wk. Antibody levels on day 4 confirmed the lack of immunization against tetanus (<0.1 kIU/L, ELISA, Laboratoires Mérieux, France).
The diagnosis of tetanus is made on clinical grounds and requires constant vigilance, especially in high-risk populations (i.e., immunocompromised patients—elderly, neonates, IV drug users, patients with human immunodeficiency virus). During tetanus, tetanospamine is transported retrogradely and disables the inhibitory α interneurons, leading to uncontrolled motor neuronal discharge and intense rigidity and spasms. Because of their short axonal pathways, the masseter muscles are often first involved in tetanus (3). However, all nerves may be affected. Thus, autonomic dysfunction and flaccid paralysis can occur in severe disease. Management of tetanus is multifaceted and includes neutralization of existing toxin with human tetanus anti-toxin, active immunization, removal of the source of infection with antibiotics and wound débridement, and supportive intensive care to minimize the adverse effects of existing toxin (rigidity, spasms, and autonomic dysfunction). The degree of supportive care required depends on the severity of the disease and may range from the relief of trismus to full intensive care unit care. Autonomic instability in severe cases complicates management and may be a cause of mortality independent of airway and respiratory events. In our case, tetanus was easily recognized because of a typical clinical history, i.e., the omission of the tetanus immunoprophylaxis guidelines in a nonimmunized elderly woman with an infected wound after contact with soil. However, this is the first report of the use of peripheral nerve block in tetanus.
Because of the patient’s poor general medical condition, a simple and safe method for opening the mouth was needed. General anesthesia using muscle relaxants was considered inappropriate because of the risks of aspiration and laryngeal spasm associated with orotracheal intubation (2). Moreover, administration of succinylcholine after the fourth day may lead to massive potassium release from the hyperstimulated muscles, causing hyperkalemia (4). Botulinum toxin has been successfully used to treat trismus (5), notably, in a patient suffering from cephalic tetanus who was able to open his mouth 1 cm 10 days after Botox injection (6). However, its delayed onset, requiring several days, would not have achieved the rapid effect required.
Mandibular nerve blocks have been successfully used for the management of bilateral trismus associated with hypoxic-ischemic encephalopathy (7). Mandibular nerve blocks can be easily performed by the extraoral approach (8,9). Nevertheless, the clinician should be aware of the anatomy of the pterygomandibular space and the rare complications that can arise. Mandibular nerve blocks have been implicated in producing neurological side effects, such as facial palsy, strabismus, diplopia, ptosis, ophthalmoplegia, and temporary blindness, likely produced by injection into the maxillary artery or the middle meningeal artery (10). We did not use a nerve stimulator, as we felt that this would be problematic in the presence of persistent muscle contractions. We believed the risk of aspiration with general anesthesia and tracheal intubation was more than the risk of intradural or vascular injection or neurologic side effects during mandibular blocks. In the present case, sedation was not administered and therefore respiratory depression was avoided. We successfully managed the trismus without administration of analgesics that could have potentially necessitated aggressive airway interventions and the attendant risks.
In summary, we suggest that mandibular nerve blocks are useful tools in the management of oral events during tetanus in conscious patients.
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