Diagnostic method for differentiating external hydrocephalus from simple subdural hygroma.
OBJECTIVE
The various terms used to describe subdural fluid collection--"external hydrocephalus", "subdural hygroma", "subdural effusion", "benign subdural collection", and "extraventricular obstructive hydrocephalus"-reflect the confusion surrounding the diagnoses of these diseases. Differentiating external hydrocephalus from simple subdural hygroma may be difficult, but the former appears to be a distinct clinical entity separate from the latter. In this report, the authors present a diagnostic method for differentiating external hydrocephalus from simple subdural hygroma, based on their clinical experience in treating subdural fluid collection after mild head trauma.


METHODS
Twenty patients with subdural fluid collection after mild head trauma were included in this study. Ventricle size was measured using a modified frontal horn index (mFHI); that is, the largest width of the frontal horns divided by the bicortical distance in the same plane, instead of the inner table distance. Bur hole trephination was performed on the appearance of a subdural fluid collection thicker than 15 mm on computed tomography (CT), persistent (longer than 4 weeks) or increasing in size, and accompanied by neurological symptoms (confusion or memory impairment). During the procedure, subdural pressure was measured using a manometer before opening the dura mater. Subdural pressure varied among the patients, ranging from 3 to 27.5 cm H2O. Four patients with a subdural pressure greater than 15 cm H2O had hydrocephalus after surgery (p < 0.05). Hydrocephalus developed in a pediatric patient (2 years old) with a subdural pressure of 12 cm H2O. All of the patients in whom hydrocephalus developed after bur hole trephination had had enlarged ventricles (mFHI > 33%) on preoperative CT scans.


CONCLUSIONS
Monitoring subdural pressure may be a valuable tool for differentiating subdural hygroma from external hydrocephalus in patients with mild head trauma. Additionally, the mFHI reflects the nature of the subdural collection more accurately than the standard frontal horn index.
Huh
Pil-Woo
PW
Department of Neurosurgery, Uijeongbu St. Mary's Hospital, The Catholic University of Korea, College of Medicine, Uijeongbu-City, Gyeonggi-do, Korea.
Yoo
Do-Sung
DS
Cho
Kyung-Suok
KS
Park
Chun-Kun
CK
Kang
Seok-Gu
SG
Park
Young-Sup
YS
Kim
Dal-Soo
DS
Kim
Moon-Chan
MC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D006259:Craniocerebral Trauma / Q000150:complications; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006849:Hydrocephalus / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013353:Subdural Effusion / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D013355:Subdural Space; D014057:Tomography, X-Ray Computed