Asphyxia
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Direct answer
Asphyxia unites a group of deaths in which oxygen delivery to the tissues fails — hanging, strangulation, suffocation, smothering, choking, compression of the chest and positional obstruction. The general autopsy signs (congestion and cyanosis of the face, petechial haemorrhages, dark fluid blood, visceral congestion) are suggestive but never diagnostic, so the diagnosis rests on the specific signs of each mechanical type: the inverted-V ligature mark of hanging, the horizontal mark of ligature strangulation, fingertip bruises of throttling and abrasions around the mouth of smothering. Cause of death in hanging, notably, is often a neurogenic cardiac arrest from vagal inhibition rather than obstruction of the airway.
What you must remember
- The hanging ligature mark is a groove that runs obliquely up the neck to the point of suspension, deepest opposite the knot, forming an inverted V — never completely encircling at the same level; the knot typically lies over the occiput in a typical hanging, and partial suspension can still kill.
- Salivary dribble from the angle of the mouth opposite the knot is a classical vital sign of hanging.
- Hyoid fracture in hanging and strangulation is an inward-compression fracture at the junction of the posterior third with the anterior two-thirds of the greater cornu; the superior cornu of the thyroid cartilage and the intima of the carotid at the bifurcation may also tear.
- Judicial hanging uses a drop calculated from body weight and produces fracture-dislocation of the second cervical vertebra (the hangman's fracture) with cord transection.
- Ligature strangulation produces a horizontal mark at or below the thyroid cartilage, usually continuous around the neck and often showing a gap at the nape where the fingers or ligature crossed.
- Manual strangulation (throttling) shows oval fingertip bruises, crescentic nail scratches and commonly hyoid injury.
- Tardieu spots are the dense subpleural and subconjunctival petechiae of asphyxia — supportive, not specific, since heart failure and clotting disorders produce them too.
- Burking is smothering combined with chest compression (Burke and Hare); traumatic asphyxia (crush) gives the engorged blue head and neck with crisp demarcation at the clavicles.
Reading a hanging scene
A young man hangs from a ceiling fan with a dupatta: suicide or concealment of homicide? At the scene, look before touching — the knot position, the feet's reach to the chair, any disturbance. On the body, the mark should be high on the neck, oblique, deepest away from the knot and fading towards it; a mark lying horizontally low across the thyroid cartilage with a crossed ligature screams strangulation first, suspension after. Check the vital signs of the event: the salivary dribble track, congestion above the ligature line, and petechiae in the conjunctivae. Then layer the neck dissection: bruising into the soft tissues and muscle under the mark, injury to the hyoid and thyroid horns, intimal tears of the carotids, and no other explanation for death.
In about a third of hangings the autopsy is essentially negative, because vagal inhibition stops the heart within a minute and leaves no time for classic asphyxial signs; then the diagnosis is one of exclusion, resting on circumstances, the direction of the mark and absence of defensive injuries. The examiner's favourite sequence — describe the mark, then say what it is not: an inverted V with a knot imprint is hanging; a horizontal band with a nape gap is strangulation; the two together demand an explanation of the order of events.
Where students slip
Petechiae are over-read as proof of asphyxia and hyoid fractures are quoted for all hangings — in fact the hyoid is fractured in only a minority of hangings (more with increasing age, as the bone ankyloses) and is far commoner in throttling. Second, candidates state that hanging kills by "airway obstruction", when the mechanisms are three — compression of the neck vessels, the airway and the vagus — and pure vagal inhibition explains the near-empty autopsy. Third, the direction and completeness of the ligature mark are the discriminating features between hanging and strangulation. Finally, in autoerotic deaths the reflex is to write suicide; the escape mechanism, padding and paraphernalia must move the verdict to accident.
Frequently asked questions
Describe the ligature mark of hanging.
An oblique, inverted-V-shaped groove running upward towards the point of suspension, deepest opposite the knot, pale hard and dry, with hyperaemia above and below; it is absent where the knot lifts the skin.
Which bone fractures in manual strangulation and at what point?
The hyoid, typically an inward compression fracture at the junction of the posterior third and anterior two-thirds of the greater cornu, from side-to-side compression.
What is the hangman's fracture?
Fracture-dislocation of the axis (second cervical vertebra) through its pedicles with spinal cord transection, produced by the calculated drop of judicial hanging.
What are Tardieu spots and their value?
Pin-head to larger subpleural and subserosal petechial haemorrhages indicating capillary rupture from raised venous pressure — supportive of asphyxia but not diagnostic of any particular type.