Correlation of MRI Findings With Patterns of Visual Field Loss in Patients With Pituitary Tumors.

BACKGROUND: Compression of the optic chiasm by pituitary tumors typically results in bitemporal hemianopia, implying that nasal retinal fibers are preferentially damaged. The reason for this is not clear. One theory suggests that nasal fibers are selectively vulnerable simply because they cross each other. This study investigated the "crossing theory" by correlating visual field (VF) loss with chiasmal elevation and with the degree of eccentric compression on MRI scans. METHODS: Our hospital database was searched to identify patients with a) chiasmal compression by a pituitary tumor; b) documented preoperative evidence of VF loss; and c) preoperative MRI scan performed within 1 month of VF testing. Temporality and bitemporality indices were derived from pattern deviation VF plots. Elevations of the central and peripheral parts of the chiasm were obtained from MRI scans, from which the eccentricity of compression was calculated. Temporality indices and hemifield loss were compared with central chiasmal elevation, and nasal hemifield loss in each eye was plotted against eccentricity. RESULTS: Eleven patients were suitable for analysis. The degree of bitemporal VF involvement was significantly correlated with elevation of the central chiasm (P = 0.004). However, there was minimal involvement of nasal VFs, and no demonstrable increase in nasal field loss with increasing eccentricity of compression. CONCLUSIONS: This study provides support for the crossing theory. These findings will inform further finite element models of chiasmal compression. A larger, prospective study is planned.

External ventricular drain infections at the Canberra Hospital: A retrospective study.

External ventricular drains (EVD) are crucial for the emergency management of hydrocephalus and raised intracranial pressure. Infection is the most morbid and costly cause of EVD malfunction and can cost up to $50,000 US to treat per case. In 2007, Canberra Hospital changed EVD management protocols requiring set-up of EVD transducer systems in theatre, cessation of prophylactic antibiotics after 24hours, cerebrospinal fluid (CSF) samples second or third daily and discontinuation of elective EVD changes. The current study aimed to retrospectively audit EVD inserted between 2006 and 2010 in order to determine the impact of these changes. There was a non-significant downward trend in infection rates from 20.93% to 11.50% (p=0.343) after the protocol changes. Patient age (OR=1.032, p=0.064, confidence interval (CI): 0.998-1.067) and sex (OR=1.405, p=0.595, CI: 0.401-4.917) were not significantly associated with infection. However, multiple drains were associated with a significant increase in infections rates (OR=21.96, p=0.001, CI: 6.103-79.023) and systemic perioperative antibiotic prophylaxis was associated with decreased rates of infections (OR=0.269, p=0.044, CI: 0.075-0.964). Our study showed a non-significant downwards trend in infections with introduction of changes to hospital protocol and illustrated some risk factors for infection in the Australian setting.

Lennox-Gastaut syndrome and idiopathic intracranial hypertension.

Lennox-Gastaut Syndrome is a severe childhood epilepsy syndrome characterised by the diagnostic triad of a slow spike and wave pattern on electroencephalogram, multiple seizure types and developmental delay. Idiopathic intracranial hypertension is a syndrome characterised by raised cerebrospinal fluid pressure in the absence of an intracranial mass lesion or ventricular dilatation and often headache. We present the first reported case of Lennox-Gastaut Syndrome associated with symptomatic idiopathic intracranial hypertension in a 15 year old male, requiring cerebrospinal fluid diversion by means of ventriculoperitoneal shunting.

A cluster of nocardial brain abscesses.

BACKGROUND: Nocardia species are aerobic Gram-positive bacteria that are ubiquitous in the environment. Infection usually occurs through inhalation or direct cutaneous inoculation of the organism. It has been reported that infection is more common in warm, dry climates. Cerebral nocardiosis is an uncommon clinical entity, representing only 2% of all cerebral abscesses. It is an illness associated with significant morbidity and mortality. CASE DESCRIPTIONS: We report 4 cases of nocardial brain abscesses presenting to TCH, Australia, within a 1-year period. All 4 cases occurred in men without any significant underlying immunocompromise. In 3 of the cases, the diagnosis was only established after craniotomy. All cases were given prolonged antimicrobial therapy. After more than 8 months of follow-up, there have been no deaths or treatment failures. There has been only one other case of nocardial brain abscess at TCH over the past 15 years. We review the current literature on cerebral nocardiosis. CONCLUSION: Nocardial brain abscesses are uncommonly encountered at our institution. This cluster of 4 cases over a 1-year period has therefore led us to postulate that the severe drought may be aiding in the transmission of the bacteria. The cases also emphasize the propensity of nocardial infections to mimic other conditions, particularly malignancy, which may lead to delays in appropriate surgical treatment and antimicrobial therapy. The diagnosis requires a high clinical index of suspicion, with early tissue and microbiological diagnosis. Prolonged antimicrobial therapy is required to prevent relapse of the infection.