Dr Macleod (February 2004 JRSM1) whilst outlining the psychiatric effects of ‘shell shock’, overlooks some important clinical and experimental evidence of direct and indirect central nervous system (CNS) injury following exposure to explosive blast. The contribution of such injury to the psychiatric manifestations is unknown but worthy of consideration.
In his three Lettsomian lectures Mott referred to the concussion or commotio cerebri produced by ‘aerial compression’,2 but probably wrongly attributed post-mortem findings of punctate haemorrhages and chromatolysis in soldiers to carbon monoxide poisoning. Further evidence of a primary blast effect on the brain was reported by Cohen and Biskind who showed scattered intracerebral and extracerebral haemorrhages in nine soldiers killed by air blast whose symptoms had included extreme restlessness, excitability and irrationality.3
Animal experimentation shows further evidence of cerebral injury following blast in air, Hooker having been the first to demonstrate focal damage to the CNS involving lethargy, paralysis and convulsions in frogs, rabbits and dogs.4 More recently, an investigation of the causes of post-traumatic stress disorder showed evidence of neuronal atrophy in the cerebral and cerebellar cortices of rats surviving exposure to the detonation of a single TNT charge in an underground bunker, these changes being maximal in animals killed on day 14.5 Axonal degeneration with chromatolysis and disruption of cellular function in the brainstem have also been observed as distant effects following penetrating ballistic injury to the thigh in pigs6 and following pulmonary blast injury in rabbits.7
Cerebral air emboli have been demonstrated in animals sustaining pulmonary injury induced by blast in air and underwater, air gaining access to the circulation by traumatic alveolar-venous fistulae.8-10 Reports of cerebral emboli in human beings are rare but emboli have been observed in retinal vessels at ophthalmoscopy in survivors of pulmonary blast injury10 and in the brains of fatalities post mortem.11,12