traumatic basal subarachnoid haemorrhage

 

 

Single punch to the head-related deaths in the media

Deaths following a single punch to the head are not infrequently reported in the media; some of these deaths result from the effects of blunt force trauma due to the fall to the ground - resulting in skull fractures, meningeal bleeding and cerebral contusions, but some are due to basal subarachnoid haemorrhage due to vertebrobasilar artery injury.

That a single blow can result in death surprises many members of the public, and has led to public health campaigns in order to raise awareness of this phenomenon (e.g. 'One punch can kill' campaign, and the 'Stop. One punch can kill' campaign).

Examples reported in the media:

 

Traumatic basal subarachnoid haemorrhage in the media

Occasionally the media report the pathologic consequences of a fatal 'single blow to the head', including traumatic basal subarachnoid haemorrhage. Many of the fatal traumatic basal subarachnoid cases involve the intracranial vertebral arteries, a difficult anatomical area to explore at autopsy.

autopsy demonstration of traumatic basal subarachnoid haemorrhage

 

In order to demonstrate and assess the vertebrobasilar arterial system in cases of suspected traumatic basal subarachnoid haemorrhage the pathologist can approach the autopsy in a number of ways.

The brain and cerebral blood vessels could be visualised using radiological techniques, including post mortem CT scanning, although the ability to visualise the vessels is somewhat limited by the absence of a circulation. Post mortem angiographic techniques are improving, and this method might supercede dissection in some cases in the future.

A technique which can reliably demonstrate injury to the vertebrobasilar blood vessels involves isolating the origin of the vertebral arteries in the base of the neck (a branch of the subclavian artery) and cannulating those arteries, allowing fluid to be gently flushed into the arteries on the base of the brain.

With the skull vault removed, and the dura reflected, the brain is retracted backwards to allow visualisation of the basilar artery, which is tied off anteriorly. The cerebral hemispheres can be removed, and the basal subarachnoid haemorrhage washed off to allow inspection of the anterior cerebral vasculature (to exclude aneurysms etc).

The tentorium cerebelli can now be reflected, and the lateral aspects of the cerebllar hemispheres removed to allow more access to the brainstem.

Removal of blood clot from the brainstem allows visualisation of the vertebral arteries, and fluid is flushed from the origins of the arteries; any abnormal escape of fluid can be identified and documented by video and/ or still photography.

The brainstem can then be removed for further examination after fixation in formalin.

Microscopy of the vertebrobasilar arteries is necessary to demonstrate the presence of a traumatic tear, and the absence of pre-existing natural disease in those blood vessels (e.g. aneurysms, vasculitis, malformations, fibromuscular dysplasia, cystic medial necrosis, segmental arterial mediolysis etc).

Toxicological analysis is necessary to determine whether any vasoactive substance is present which might have a bearing on vascular injury, such as cocaine/ amphetamine etc.

mechanism of death in fatal traumatic basal subarachnoid haemorrhage

 

There is nothing in the forensic medical literature to suggest that spontaneous tears of healthy intracranial vertebral arteries can occur; tearing of healthy vessels are reported in association with injury.

The criteria for ascribing vertebral artery tears to injury described by Leadbeatter (1994) are:

  • there is a history of trauma;
  • there is a correlation in time between trauma and collapse and/ or death;
  • there is pathological evidence of injury to a blood vessel which may be a source of subarachnoid haemorrhage, the injury having appearances in keeping with infliction at the time of trauma; and
  • there is absence of pre-existing natural disease within that blood vessel.

Subarachnoid haemorrhage as a cause of cardiorespiratory arrest has been confirmed by Tabbaa et al (1987). It is thought that the rapid escape of blood into the subarachnoid space around the brainstem causes pressure to be exerted in the areas of cardiorespiratory centres. The presence of subarachnoid blood may also invoke vasospasm of vessels supplying those vital centers.

The most common manner in which vertebral artery injury is reported to occur in the forensic medical literature is a blow to the head and/ or neck, often followed by a collapse or fall to the ground (for example Coast and Gee 1984, Deck and Jagadha 1986, and Gray et al 1999).

A blow to the head/ upper neck - at the level of the skull base/ around the mastoid region in particular - is thought to cause a complex movement of the head on the neck - rapid extension and rotation - which causes vertebrobasilar artery injury.

Why this occurs in some individuals and not others is not understood, although there is some evidence to suggest that vulnerability to traumatic vascular injury might be present in those individuals with a type 3 procollagen gene mutation (COL3A1 - Pickup and Pollanen 2011).

It has also been suggested that the avoidance of a blow may also result in a similar complex movement of the head on the neck resulting in vertebral artery injury (Leadbeatter 1994).

An issue which is often raised in these cases is 'could the vertebral artery injury have occurred not as a consequence of a blow to the head, but from the subsequent fall to the ground?'. There are, however, insufficient numbers of cases - reported in sufficient detail - in the literature to completely exclude this possibility.

Traumatic vertebral artery injuries are most commonly described as occurring on the same side as the injurious blow to the head and/ or neck. In the majority of cases, collapse and sustained loss of consciousness or death occur immediately - or rapidly - following the injurious insult.

The forensic medical literature describes an association between alcohol intoxication and traumatic basal subarachnoid haemorrhage, although Leadbeatter (1994) describes the role of alcohol in such cases as 'impossible to clarify'.

It could be that alcohol reduces muscular tone in the neck muscles, allowing the complex movement of the head and neck thought to be responsible for vertebral artery injury to occur, rather than any direct effect on the vessels themselves.

The classic scenario of deaths due to traumatic basal subarachnoid haemorrhage involves individuals who have been drinking alcohol, and public health campaigns aimed at warning people of the dangers of a single punch to the head whilst out drinking should be encouraged.

 

additional resources

 

Anatomy

 

The Circle of Willis (gross anatomy illustration)

 

 

 

Anatomy for Emergency Medicine 02: The Vertebral Artery from Andy Neill on Vimeo.

 

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