Authorities in Long Island have studied a publication by the World Health Organization (WHO) called the International Classification of Diseases (ICD). In this publication, trauma and head injury are included in the chapter ‘Injury and Poisoning’. Before 1950, trauma was classified by the external cause, which makes it impossible to collect data regarding only injuries to the head. The fifth version, ICD-5, added a classification based on the nature and diagnosis of the injury.
Still, all brain injuries were classified as ‘Intracranial injury without skull fracture’, which included hematomas of the scalp – not necessarily a brain injury. This focused on such problems as skull fractures, rather than impacts that might damage the brain without causing significant damage to the skull itself.
The ninth edition, ICD-9-CM, provided a three-digit code system for major diagnostics, such as 800 meaning skull fractures. An additional digit, such a 800.1 – Closed head injury with cerebral laceration and contusion; 800.2 – Closed head injury with subarachnoid, subdural, and extradural hemorrhage, serve to further classify injuries and diseases. The CM stands for Clinical Modification, which could add yet another digit, to provide further definition.
The ICD system is used by many countries for the standard of public health data collection, as well as most hospitals for the case of diagnostic or treatment coding, when it comes to recording and retrieving data. ICD-based studies of head injury are, of course, population-based and tend to be national, local, or hospital-based. Like all databases there can still be human error involved. In some cases the ICD coding of external causes of injury had been left out of the majority of a group of eye injuries in Brooklyn, United States.