A healthy young man dives headfirst into a mountain stream on a hot summer day and floats motionless moments later. Autopsy shows no water in the airways and no signs of struggle. Which mechanism explains his death?
- A Cervical spinal cord injury from impact against a submerged rock
- B Acute pulmonary oedema from negative pressure inspiration underwater
- C Reflex vagal inhibition of the heart from stimulation of trigeminally innervated surfaces by cold water ✓
- D Exertional heat stroke with cardiovascular collapse
Correct answer: C. Reflex vagal inhibition of the heart from stimulation of trigeminally innervated surfaces by cold water
Explanation
This is immersion syndrome or hydrocution. Sudden contact of cold water with the face, nasal and pharyngeal mucosa, or the tympanic membrane stimulates branches of the trigeminal nerve, triggering intense vagal discharge that arrests the heart. Death occurs within seconds, so no water is inhaled and there are no signs of struggle or aspiration. Spinal injury would show vertebral and cord trauma at autopsy, which the stem excludes.
Reference: Parikh's Textbook of Medical Jurisprudence, Forensic Medicine and Toxicology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.