Making an objective diagnosis of tetanus—utility of a simple neurophysiological test

Tetanus remains a significant cause of mortality especially in the developing world. Early diagnosis and institution of treatment is critical to prevent fatal complications. The diagnosis is made on clinical grounds, which may sometimes be difficult, especially in case of localised tetanus. Being able to diagnose tetanus objectively is invaluable in such cases. In this regard, masseter inhibitory reflex (MIR) is a simple neurophysiological test that can be performed at the bedside. Herein, we report a case of craniocervical tetanus that was objectively diagnosed using MIR and adequately treated.

Cranial Reflexes and Related Techniques

Electrophysiological study of the function of cranial nerves, particularly the fifth and seventh cranial nerves, may be useful for assessing cranial neuropathies or facial movement disorders, such as hemifacial spasm or facial synkinesis. Several electrophysiological techniques are available in clinical neurophysiology laboratories to study these nerves and cranial reflexes. These techniques can also provide useful information in some cases of peripheral neuropathy, polyradiculoneuropathy, and brain stem lesions. This chapter reviews the concepts, methods, and applications of cranial reflexes, including the blink reflex, the jaw jerk (or masseter reflex), and the masseter inhibitory reflex (MIR). Two additional techniques—one to assess a sensory nerve in the head that is not a cranial nerve of branchial arch origin, the great auricular sensory nerve, and the other to interrogate trigeminal sensory pathways from the sensory receptor level to the parietal cortex, contact heat evoked potentials—are also discussed.