Methods of neurological investigation

Abstract

Conventionally, routine skull radiography includes lateral, anteroposterior, postero-anterior and vertico-submental views. Even before the advent of modern imaging techniques, the value of skull radiography in the investigation of common neurological disorders had been questioned[1]. For example, among 100 patients with migraine, 59 had had skull films performed, all of which were normal. Similarly, in 100 patients with non-specific headache, skull X-ray was negative in all 75 in whom it was performed. A prospective study of 200 consecutive outpatients, in whom physical signs were lacking, concluded that a single lateral skull film had provided no diagnostically useful information [1]. Other than medical criteria may influence the decision to perform skull X-rays. In a study published in 1979, it was estimated that 75% of all non-hospital radiological studies in the USA were performed by non-radiologists [2]. An analysis revealed that the non-radiologist physician who owned an X-ray machine used an average of twice as many X-ray examinations as did colleagues who referred patients to radiologists. In a prospective study of skull X-rays performed over a five month period at the UCLA Emergency Medical Centre, 19% had been ordered primarily for medicolegal purposes [3]. Indeed, perhaps the sole remaining debate concerning the use of skull radiography centres on its value in the patient with head injury. Whilst an argument could be advanced for the replacement of skull radiography by CT scanning, the fact that the former was costed at some 11% of the latter in 1977 effectively eliminates that solution [4]. Amongst 1500 successive head-injured patients, skull X-ray revealed a fracture in 93 [5]. Factors not associated with fracture included drowsiness, headache, seizures and the presence of a scalp haematoma; 21 factors were found to be significantly associated with a skull fracture. If the presence of any one of these factors had been made the criterion for performing skull films then only one of the 93 fractures would not have been detected. Moreover, 434 patients would not have required skull films, i.e. 29% of the total. Extrapolation for the whole of the USA suggested a potential annual saving of $15 000 000. A further argument against the universal use of skull X-ray in head injury is the poor correlation between the findings and those revealed by CT scanning. In one survey of head-injured adults, 32% with a significant intracranial abnormality on CT had normal skull films, whereas in 23% of those with a skull fracture, no significant intracranial CT change occurred [6]. Proponents of routine skull films in head injury remain, however, based on the evidence, from over 5000 cases, that the finding of a skull fracture accompanied by disorientation in a head-injured patient, by stimulating immediate CT scanning, would have identified two-thirds of all traumatic intracranial haematomas [7].