From confusion to coma: a catastrophic deterioration
Q1: What does figure 1 show and what is the differential diagnosis?
Figure 1 (p 52) shows a ring enhancing lesion with surrounding oedema in the left frontal lobe. Given the clinical features of pyrexia and also the raised white cell count, the most likely diagnosis is cerebral abscess. Other conditions to consider in the differential diagnosis include primary and secondary neoplasms.
Q2: How does figure 2 relate to the change in the patient's clinical condition?
Figure 2 (p 52) shows the abscess communicating and discharging, through a tract, into the ipselateral ventricle. Intraventricular rupture of an abscess is usually a catastrophic event leading to ventriculitis and dissemination of organisms throughout the cerebrospinal fluid pathway.1 This event accounts for the calamitous deterioration in the patient's clinical condition.
Q3: Discuss the management of this condition.
Improvements in imaging techniques, particularly the development of contrast enhanced CT scanning and its recommended use before lumbar puncture in patients with meningism, advances in neurosurgery and especially stereotaxy, availability of more effective antibiotics, and better neurointensive care facilities have resulted in a substantial reduction in mortality from brain abscess.1Intraventricular rupture of a cerebral abscess, however, continues to be a devastating event, carrying mortality rates of up to 85%.2-4
Delay in diagnosis and subsequent neurosurgical referral are important risk factors for this condition. The main diagnostic problem is differentiation of a cerebral abscess from a ring enhancing tumour. Although not absolute, however, certain features may favour the former diagnosis: Abscesses tend to be sited in the vascular watershed regions, often having a thin, smooth, enhancing wall which is in contrast to the thick, irregular, diffuse enhancement seen with tumours.1 Once suspected, all abscesses require urgent neurosurgical assessment, but perhaps the urgency is greater in those located close to the ventricular system because of the risk of intraventricular rupture.
Once ruptured, the prognosis of such patients remains poor. Both stereotactic aspiration and craniotomy and evacuation of the abscess, with variable results, have been reported.2 5 Most neurosurgeons also advocate insertion of an external ventricular drain to allow both drainage of contaminated cerebrospinal fluid and direct administration of intrathecal antibiotics.2 4 The choice of antibiotics is crucial and often entails initial treatment with broad spectrum antibiotics followed by more specific antimicrobial treatment once culture and sensitivity results from the abscess aspirate are available. The optimum duration of antibiotic treatment is not clear but most recommend at least six weeks.2
In the case described here, the patient already had severe neurological compromise with fixed and dilated pupils by the time of arrival at the neurosurgical unit. An urgent stereotactic aspiration of the abscess was performed and an external ventricular drain was inserted to allow drainage of infected CSF. Gram stain of the aspirate from the abscess showed both Gram positive cocci and rods. The patient was started on a combination of intravenous benzylpenicillin, cefotaxime, vancomycin, and metronidazole, as well as intrathecal vancomycin. Despite this treatment, however, the patient continued to deteriorate and died shortly after. CSF culture results later showedStreptococcus milleri andActinomyces meyeri, both sensitive to penicillin.
Proximity of an intracerebral abscess to the ventricular system warrants particularly urgent neurosurgical attention.