Tetanus toxin blocks the relaxation pathway in muscles, causing which clinical feature?

• A. Flaccid paralysis
• B. Sustained muscle spasms and rigidity
• C. Loss of consciousness
• D. Fever with rash

Answer: (B)

Tetanus toxin leads to unopposed muscle excitation by blocking the normal inhibitory signals that keep muscles relaxed. The toxin (tetanospasmin) travels into the spinal cord and prevents the release of inhibitory neurotransmitters glycine and GABA from interneurons. Without this inhibition, motor neurons fire continuously, causing sustained, painful muscle contractions and rigidity. This produces the classic picture of prolonged spasms and stiffness, including lockjaw and generalized rigidity. Loss of consciousness and fever with rash aren’t typical features of tetanus. In contrast, flaccid paralysis is characteristic of botulinum toxin, which blocks acetylcholine release at the neuromuscular junction.