Diffusion tensor imaging and ventricle volume quantification in patients with chronic shunt-treated hydrocephalus: a matched case-control study

OBJECTIVEThe object of this study was to use diffusion tensor imaging (DTI) and tract-based spatial statistics (TBSS) to characterize the long-term effects of hydrocephalus and shunting on white matter integrity and to investigate the relationship of ventricular size and alterations in white matter integrity with headache and quality-of-life outcome measures.METHODSPatients with shunt-treated hydrocephalus and age- and sex-matched healthy controls were recruited into the study and underwent anatomical and DTI imaging on a 3-T MRI scanner. All patients were clinically stable, had undergone CSF shunt placement before 2 years of age, and had a documented history of complaints of headaches. Outcome was scored based on the Headache Disability Inventory and the Hydrocephalus Outcome Questionnaire. Fractional anisotropy (FA) and other DTI-based measures (axial, radial, and mean diffusivity; AD, RD, and MD, respectively) were extracted in the corpus callosum and internal capsule with manual region-of-interest delineation and in other regions with TBSS. Paired t-tests, corrected with a 5% false discovery rate, were used to identify regions with significant differences between patients and controls. Within the patient group, linear regression models were used to investigate the relationship between FA or ventricular volume and outcome, as well as the effect of shunt-related covariates.RESULTSTwenty-one hydrocephalus patients and 21 matched controls completed the study, and their data were used in the final analysis. The authors found significantly lower FA for patients than for controls in 20 of the 48 regions, mostly posterior white matter structures, in periventricular as well as more distal tracts. Of these 20 regions, 17 demonstrated increased RD, while only 5 showed increased MD and 3 showed decreased AD. No areas of increased FA were observed. Higher FA in specific periventricular white matter tracts, tending toward FA in controls, was associated with increased ventricular size, as well as improved clinical outcome.CONCLUSIONSThe study shows that TBSS-based DTI is a sensitive technique for elucidating changes in white matter structures due to hydrocephalus and chronic CSF shunting and provides preliminary evidence that DTI may be a valuable tool for tailoring shunt procedures to monitor ventricular size following shunting and achieve optimal outcome, as well as for guiding the development of alternate therapies for hydrocephalus.

Bulbar dysfunction in normal pressure hydrocephalus: a prospective study

OBJECTIVE Normal pressure hydrocephalus (NPH) is clinically characterized by gait disturbance, cognitive impairment, and urinary incontinence, as well as enlargement of the ventricles. To the best of the authors' knowledge, there have been no previous publications regarding the correlation between bulbar dysfunction and NPH. The primary objective of this study was to compare preoperative and postoperative prevalence of bulbar dysfunction in patients with NPH. Secondary objectives included assessing the results of surgery for swallowing, speech, gait, cognition, and urination, and evaluating the correlation between bulbar dysfunction and triad symptoms. METHODS Fifty-three patients with NPH who underwent shunt placement surgery at Siriraj Hospital were included in the study. Patients were evaluated for gait, cognition, urination, swallowing, and speech before and 6 months after shunt placement. Triad symptoms were assessed using standard methods. Bulbar dysfunctions were assessed using the Swallowing Problem Questionnaire, Thai Articulation Test, Resonation Screening Test (RST), and Thai Nasality Test. The Thai Speech Assessment Program and nasometer were used for objective speech measurement. RESULTS Preoperatively, 86% (43/50) of patients had swallowing problems and 75% (37/49) had speech problems, as measured by the RST. Postoperatively, there was significant improvement in swallowing (p < 0.001), speech problems by RST (p = 0.008), and voice volume (p = 0.009), but no significant change in the nasometer test. All triad symptoms were improved. There were significant correlations between swallowing impairment and gait disturbance (r = 0.358, p = 0.009), and RST and cognitive impairment (r = -0.502, p < 0.001). CONCLUSIONS This is the first study of bulbar dysfunction in patients with NPH. The results showed that the prevalence of bulbar dysfunction is very high. The correlation between bulbar dysfunction and the classic NPH triad has been documented and published. These bulbar symptoms also significantly improved after surgery. As such, bulbar dysfunction should be regarded as a core symptom that should be considered along with the classic triad in the clinical diagnosis and management of NPH.

Contemporary model of language organization: an overview for neurosurgeons

Classic models of language organization posited that separate motor and sensory language foci existed in the inferior frontal gyrus (Broca's area) and superior temporal gyrus (Wernicke's area), respectively, and that connections between these sites (arcuate fasciculus) allowed for auditory-motor interaction. These theories have predominated for more than a century, but advances in neuroimaging and stimulation mapping have provided a more detailed description of the functional neuroanatomy of language. New insights have shaped modern network-based models of speech processing composed of parallel and interconnected streams involving both cortical and subcortical areas. Recent models emphasize processing in "dorsal" and "ventral" pathways, mediating phonological and semantic processing, respectively. Phonological processing occurs along a dorsal pathway, from the posterosuperior temporal to the inferior frontal cortices. On the other hand, semantic information is carried in a ventral pathway that runs from the temporal pole to the basal occipitotemporal cortex, with anterior connections. Functional MRI has poor positive predictive value in determining critical language sites and should only be used as an adjunct for preoperative planning. Cortical and subcortical mapping should be used to define functional resection boundaries in eloquent areas and remains the clinical gold standard. In tracing the historical advancements in our understanding of speech processing, the authors hope to not only provide practicing neurosurgeons with additional information that will aid in surgical planning and prevent postoperative morbidity, but also underscore the fact that neurosurgeons are in a unique position to further advance our understanding of the anatomy and functional organization of language.