Rigor mortis
Rigor mortis (Cadaveric Rigidity or Death Stiffening)
- It is defined as contraction, stiffening, shortening and opacity of muscles after death.
- It occurs after molecular (cellular) death.
Time of Onset :
- Temperate climates – 3-6 hours
- Tropical climates – 1-2 hours
Duration
- Temperate climate –
- lasts for 2-3 days.
- Tropical climate –
- 24 – 48 hours in winter
- 18 – 36 hours in summer
- In general –
- 1-2 hours sets on
- for , 12 hours develop
- for – 12 hours maintains
- and after 12 hours passes off
Pattern
- Rigor mortis generally occurs when body is cold.
- Not related to nerves action
- Develops in paralysed limbs also
- First appear in involuntary muscles
- However, it does not start in all muscles simultaneously (nysten’s rule).
- Involuntary muscles (heart) are involved first than voluntary muscles.
- Sequence of muscles involvement is as follows : Heart> upper eyelid> neck >jaw > face > chest > upper limb > abdomen > lower limb > finger and toes.
- It passes off in the same order in which it has appeared.
Factors affecting rigor mortis
Rigor mortis is not seen :
- Fetus < 7 months
- epticemic conditions.
Appears early and passes off quickly :
- Chronic diseases (TB, cancer, typhoid, cholera)
- Convulsive disorders (strychnine poisoning )
- Violent deaths (cut throat, electrocution, lightening).
Early onset and last longer :
- Drowning and strychnine poisoning
Early onset :
- Organophosphate poisoning, cholera, heat stroke and fatigue/exhaustion before death
Delayed onset :
- Asphyxia, apoplexy, severe haemorrhage, pneumonia and paralysis of muscles.
Lasts longer or delayed disappearance :
- CO poisoning
- Arsenic poisoning
Early disappearance :
- Widespread bacterial infection, e.g., gas gangrene.
Cadaveric spasm (instantaneous rigor)
- Is defined as the condition wherein a group of muscles, which were in contraction or spasm at the time of death, continue to be in spasm even after death, without the stage of primary relaxation.
Exam Important
Rigor mortis (Cadaveric Rigidity or Death Stiffening)
- It is defined as contraction, stiffening, shortening and opacity of muscles after death.
Time of Onset :
- Temperate climates – 3-6 hours
- Tropical climates – 1-2 hours
Duration
- Temperate climate – lasts for 2-3 days.
- Tropical climate – 24 – 48 hours in winter,18 – 36 hours in summer
Pattern
- First appear in involuntary muscles
- However, it does not start in all muscles simultaneously (nysten’s rule).
- Involuntary muscles (heart) are involved first than voluntary muscles.
- Sequence of muscles involvement is as follows : Heart> upper eyelid> neck >jaw > face > chest > upper limb > abdomen > lower limb > finger and toes.
- It passes off in the same order in which it has appeared.
Factors affecting rigor mortis
- Rigor mortis is not seen : Fetus < 7 months
- Appears early and passes off quickly : Chronic diseases (TB, cancer, typhoid, cholera), Convulsive disorders (strychnine poisoning ),Violent deaths (cut throat, electrocution, lightening).
- Early onset and last longer : Drowning and strychnine poisoning
- Early onset : Organophosphate poisoning, cholera, heat stroke and fatigue/exhaustion before death
- Delayed onset :Asphyxia, apoplexy, severe haemorrhage, pneumonia and paralysis of muscles.
- Lasts longer or delayed disappearance : CO poisoning and Arsenic poisoning
- Early disappearance : Widespread bacterial infection, e.g., gas gangrene.
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