Review of the literature produces conflicting findings, with some authors advocating emergency neuroimaging on all HIV-positive patients, and some reliance on clinical signs as indications for emergency neuroimaging. Furthermore, few authors differentiate between generalised seizures and focal seizures.

Barber et al. noticed that the majority of urgent cranial CT requests for HIV-infected patients at their hospital was motivated by clinicians believing that immune-compromised patients might have focal intracranial sepsis without the usual clinical signs. Barber et al. gained the impression that many of these scans were normal, and they investigated whether clinical signs were helpful in pointing to patients who harboured intracranial pathology. The authors divided their study sample into two groups: HIV-positive patients, and patients with acquired immune deficiency syndrome (AIDS). In the HIV-positive group, no patient had treatable intracranial pathology without focal neurological signs. In the AIDS group, the majority of patients with treatable intracranial disease presented with either seizures (no differentiation was made between generalised or focal seizures) or focal neurology. However, two patients in the AIDS group had treatable intracranial disease, and only presented with headache or diffuse cerebral dysfunction, without focal neurology. The authors thus suggested that clinical signs remain useful for deciding whether urgent CT was appropriate.¹

Rothman et al. attempted to correlate neurological signs and symptoms with new focal intracranial lesions in HIV-positive patients. The authors found that NOS was strongly associated with intracranial lesions; however, no differentiation was made between generalised and focal seizures.²

Holtzman et al. retrospectively reviewed 100 cases of NOS in HIV-positive patients. In this case series, mass lesions were found to be the most common cause of NOS in the HIV-positive population. Of note, however, is the fact that all the patients who presented with generalised seizures and a normal neurological examination either had meningitis, or no identifiable cause of their seizures could be identified. The authors further suggested that, despite the seizure type, a normal neurological examination implied a low probability of identifying an underlying cause for NOS.⁴

Modi et al. at the University of the Witwatersrand evaluated 37 HIV-infected patients with NOS with regards to seizure type, CD4 count and viral load. All patients for whom no identifiable cause for seizures could be determined presented with generalised seizures; however, 48% of the patients with focal brain lesions also presented with generalised seizures. The authors did not report whether the patients with focal brain lesions had co-existing focal neurology.⁵

The most specific research regarding generalised seizures in HIV-positive patients was done on a sample of 26 patients by Pesola et al. in 1998. They studied the aetiology of generalised NOS in patients with AIDS who presented at their emergency department. Six (43%) of their patients necessitated emergency clinical management (requiring immediate hospitalisation and treatment); five were suffering from central nervous system (CNS) toxoplasmosis and one with CNS lymphoma. Notably, only two of these patients presented with focal neurology, and the authors therefore recommended emergency neuroimaging on all HIV-positive patients with generalised seizures, regardless of neurological examination findings.⁶ It is worth noting that the authors only investigated patients with a CD4 count < 200 cells/mm³ (AIDS defining, according to the Centers for Disease Control and Prevention (CDC) staging system).

The incidence of NOS in the HIV-positive population has been reported to be as high as 17%^7,8 (or even 20%, as reported by Satishchandra et al., although selection bias might have been present because their hospital is an independent neurological referral centre).⁹ Furthermore, most of these patients present with generalised seizures, at a percentage as high as 71%.^{4,5,8,9,10,11} Obtaining emergency neuroimaging in so many of the patients could potentially overload emergency and radiology departments.

We conducted a prospective descriptive observational study. Approval was obtained from the ethics committee of the Faculty of Health Sciences of the University of the Free State, as well as the clinical director of Kimberley Hospital Complex. Informed consent was obtained from either the patient or a family member. Data were collected from October 2014 to September 2015.

Consecutive HIV-positive patients ≥ 18 years old who presented to Kimberley Hospital Complex emergency department within 24 hours of their first generalised seizures and who had a normal post-ictal neurological examination, were included.

Patients known to suffer from epilepsy, who had suffered any previous seizure (with or without secondary generalisation), who had any contra-indication to CT, or for whom there was clinical uncertainty, were excluded from the study.

Patients who met the inclusion criteria for the study received a CT within 8 hours of clinical presentation, according to the Kimberley Hospital Rule.³

Patients with clinically suspected HIV infection received confirmatory laboratory testing with pre- and post-test counselling. If a patient’s recent CD4 count was not known, it was obtained during admission.

The CD4 count results were divided into three groups, namely, CD4 counts < 200 cells/mm³, > 200 cells/mm³ ≤ 499 cells/mm³, and > 500 cells/mm³, in accordance with the CDC classification system.

Cranial CT was reported by a radiology registrar, with findings confirmed by a qualified radiologist; the differential diagnosis was completed on the datasheet. Decision to administer iodinated contrast was based on non-contrast CT findings. It was also noted whether the CT findings changed the emergency management (i.e. immediate hospitalisation and treatment).

Descriptive statistics, namely median and ranges, were calculated for continuous data. Frequencies and percentages were calculated for categorical data.