Intranuclear ubiquitin immunoreactivity of the pigmented neurons of the substantia nigra in fatal acute mechanical asphyxiation and drowning

To evaluate the significance of immunohistochemical staining of ubiquitin (heat shock protein) in the midbrain for the medico-legal diagnosis of fatal asphyxiation and drowning, we investigated forensic autopsy cases of fatal mechanical asphyxia (n = 18), manual/ligature strangulation (n = 9), hanging (n = 4), aspiration/choking (n = 5) and drowning (n = 16). These were compared to control groups (n = 30) consisting of fatalities from brainstem injury (n = 12) and acute myocardial infarction (n = 18). Ubiquitin was clearly demonstrated in the nuclei of pigmented substantia nigra neurons, showing two intranuclear staining patterns: a type of inclusion (possibly Marinesco bodies) and a diffuse staining. The diffuse staining was significantly more frequently observed in cases of drowning. The percentage of total ubiquitin positive neurons was frequently higher in strangulation (5.1-28.4%, mean 17.0%), aspiration/choking (5.3-32.0%, mean 17.6%) and drowning (7.0-34.1%, mean 19.8%), but relatively low in hanging (5.1-12.7%, mean 8.6%), brainstem injury (0-10.4%, mean 5.0%) and acute myocardial infarction (1.5-16.9%, mean 8.3%). These observations suggest that intranuclear ubiquitin immunoreactivity of the pigmented substantia nigra neurons in the midbrain was induced by a fatal severe stress on the central nervous system in asphyxiation and drowning.