Brain volume changes in spontaneous intracranial hypotension: Revisiting the Monro-Kellie doctrine

Objectives In the application of the Monro-Kellie doctrine in spontaneous intracranial hypotension, the brain tissue volume is generally considered as a fixed constant. Traditionally, cerebral venous dilation is thought to compensate for decreased cerebrospinal fluid. However, whether brain tissue volume is invariable has not yet been explored. The objective of this study is to evaluate whether brain tissue volume is fixed or variable in spontaneous intracranial hypotension patients using automatic quantitative methods. Methods This retrospective and longitudinal study analyzed spontaneous intracranial hypotension patients between 1 January 2007 and 31 July 2015. Voxel-based morphometry was used to examine brain volume changes during and after the resolution of spontaneous intracranial hypotension. Brain structure volume was analyzed using Statistical Parametric Mapping version 12 and FMRIB Software Library v6.0. Post-treatment neuroimages were used as surrogate baseline measures. Results Forty-four patients with spontaneous intracranial hypotension were analyzed (mean [standard deviation] age, 37.8 [8.5] years; 32 female and 12 male). The whole brain tissue volume was decreased during spontaneous intracranial hypotension compared to follow-up (1180.3 [103.5] mL vs. 1190.4 [93.1] mL, difference: −10.1 mL [95% confidence interval: −18.4 to −1.8 mL], p = 0.019). In addition, ventricular cerebrospinal fluid volume was decreased during spontaneous intracranial hypotension compared to follow-up (15.8 [6.1] mL vs. 18.9 [6.9] mL, difference: −3.2 mL [95% confidence interval: −4.5 to −1.8 mL], p < 0.001). Longer anterior epidural cerebrospinal fluid collections, as measured by number of vertebral segments, were associated with greater reduction of ventricular cerebrospinal fluid volume (Pearson’s r = −0.32, p = 0.036). Conclusion The current study found the brain tissue volume and ventricular cerebrospinal fluid are decreased in spontaneous intracranial hypotension patients. The change in ventricular cerebrospinal fluid volume, but not brain tissue volume change, was associated with the severity of spinal cerebrospinal fluid leakage. These results challenge the assumption that brain tissue volume is a fixed constant.

Neurophysiological evaluation of canine congenital hydrocephalus in three dogs

Congenital hydrocephalus is a neurological disorder frequently observed in dogs. It is characterised by an increase of cerebrospinal fluid volume in the ventricular system that can cause atrophy of brain tissue. It can be provoked by diverse causes, as it can be idiopathic or secondary to nervous system abnormalities. Diagnosis is based on clinical signs and imaging studies, but neurophysiological techniques can provide valuable information. This report describes functional changes in the brain and brainstem evaluated by electroencephalogram and auditory evoked potentials. In the three cases, the authors found alterations in background rhythm, slow waves, epileptiform activity, hypsarrhythmic tracing and positive sharp waves. These techniques allow detecting alterations in the brain bioelectrical activity that do not trigger clear clinical responses.