The majority of cases have an unknown cause. Factors such as chronic pharyngitis, excessive and prolonged use of tobacco and alcohol, irritation from physical and chemical stimuli, prolonged stimulation of the pharynx by nasal secretions, idiopathic muscle spasm, and idiopathic tremor can all contribute to the occurrence of pharyngeal muscle spasm. The causes of pharyngeal muscle paralysis can also lead to pharyngeal muscle spasm, which itself often serves as a precursor to paralysis.
Clinical Manifestations
Two types of pharyngeal muscle spasms are seen: tonic spasm and rhythmic spasm.
Tonic Pharyngeal Muscle Spasm
This commonly occurs in conditions such as rabies, tetanus, epilepsy, meningitis, and hysteria. Severe cases may involve symptoms like lockjaw or difficulty opening the mouth, while milder cases may exhibit swallowing difficulties, pharyngeal discomfort, gagging, or retching.
Rhythmic Pharyngeal Muscle Spasm
This is often secondary to lesions in the brainstem or lower olive region. This type features regular or irregular contraction of the soft palate and pharyngeal muscles, occurring at a frequency of 60–100 times per minute, independent of pulse and respiration. It persists during sleep and under anesthesia. During episodes, both the patient and others may perceive a "clucking" sound, described as objective tinnitus. Idiopathic tremor, Parkinson’s disease, and hyperthyroidism can also manifest as rhythmic tremor.
Diagnosis
Effortful speech, voice tremor, or inability to produce sound are indicative features, though routine examinations of the pharynx and larynx may fail to reveal muscle spasm. A thorough medical history should be obtained, and consultation with relevant specialties is recommended when necessary. X-ray barium swallow examinations can reveal swallowing difficulties caused by spasm, while fiberoptic laryngoscopy or esophagoscopy can help exclude obstructions due to organic lesions.
Treatment
Patients should receive detailed explanations of their condition to alleviate concerns and reduce psychological stress. Non-irritating foods should be consumed slowly. Different medications may be chosen based on the underlying cause and severity of the condition. Sedative and antispasmodic drugs such as baclofen are useful, and muscle relaxants like d-tubocurarine or succinylcholine may be considered for more severe cases. Hysteria patients can benefit from suggestion therapy, psychotherapy, or acupuncture combined with suggestion. If the spasm is caused by an organic lesion, treatment should focus on the underlying condition.