Ventriculoperitoneal shunting of idiopathic normal pressure hydrocephalus increases midbrain size: a potential mechanism for gait improvement.
OBJECTIVE
Idiopathic normal pressure hydrocephalus (INPH) is characterized by a classic clinical triad of symptoms, including dementia, urinary incontinence, and gait disturbance. Recent work has demonstrated that the maximal midbrain anteroposterior (AP) diameter is significantly smaller in patients with INPH than in healthy, age-matched controls. The current study was undertaken to determine the effect of ventriculoperitoneal shunt placement on midbrain dimensions in INPH patients.


METHODS
Twelve consecutive INPH patients undergoing ventriculoperitoneal shunt placement with pre- and postoperative computed tomographic scans at the Columbia University Medical Center were enrolled. Each patient's pre- and postoperative maximum AP and left-to-right diameters of the midbrain at the pontomesencephalic junction were independently measured in a blinded fashion by two of the authors. The average value of each dimension was computed by calculating the mean values of the measurements of the two observers.


RESULTS
Both the mean AP diameter (preoperative mean, 2.06 +/- 0.04 cm; postoperative mean, 2.27 +/- 0.05; P = 0.0007) and left-to-right diameter (preoperative mean, 2.80 +/- 0.07; postoperative mean, 3.03 +/- 0.08; P = 0.0029) increased from pre- to postoperative imaging. The approximate cross-sectional area determined as the product of AP and left-to-right diameters also increased from pre- to postoperative images (preoperative mean, 5.79 +/- 0.22 cm; postoperative mean, 6.90 +/- 0.25 cm; P = 0.00049).


CONCLUSIONS
This study provides supportive evidence that midbrain cytoarchitecture may play a role in the pathophysiology and post-ventriculoperitoneal shunt gait improvement of INPH patients.
Mocco
J
J
Department of Neurological Surgery, Columbia University, New York, New York 10032, USA. jdm32@columbia.edu
Tomey
Matthew I
MI
Komotar
Ricardo J
RJ
Mack
William J
WJ
Frucht
Steven J
SJ
Goodman
Robert R
RR
McKhann
Guy M
GM
D000368:Aged; D005260:Female; D005684:Gait; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D008636:Mesencephalon / Q000000981:diagnostic imaging*; D011184:Postoperative Period; D011300:Preoperative Care; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed; D017287:Ventriculoperitoneal Shunt