Page 130 - Zoo Animal Learning and Training

14 Shunt Placement and Marsupialization

in Treatment of Hydrocephalus

and Quadrigeminal Diverticula

William Thomas and Jill Narak

Hydrocephalus development in which the obstructive lesion later resolves, leaving
Hydrocephalus is active distension of the ventricular system of the only the ventricular enlargement. Pediatric hydrocephalus may also
brain caused by obstruction of flow of cerebrospinal fluid (CSF) be associated with other malformations such as meningomyelocele,
from its point of production to its point of absorption. Obstruction Chiari‐like malformation, Dandy–Walker syndrome, and arachnoid
can be caused by developmental abnormalities or acquired lesions diverticula. Signs of pediatric hydrocephalus include an enlarged
such as neoplasia or inflammatory lesions. A number of conditions dome‐shaped head with persistent fontanelles and open cranial
such as infarction and necrosis can result in decreased volume of sutures. There may be ventral or ventrolateral strabismus, due to
brain parenchyma in which the loss of brain tissue leaves a vacant either malformation of the orbit or brainstem dysfunction.
space filled passively with CSF. Although this was previously called Neurological deficits include abnormal behavior, cognitive dys-
hydrocephalus ex vacuo, such conditions do not cause active dis- function (such as inability to become house‐trained), disturbed
tension of the ventricles and are therefore not classified as hydro- consciousness, ataxia, circling, blindness, seizures, and vestibular
cephalus and do not require specific treatment [1]. dysfunction. Affected patients are often fragile and can worsen later
Definitive treatment of hydrocephalus is directed at the underly- in life coincident with other diseases or minor head trauma.
ing cause if possible. Medical therapy is used to delay surgery, to Acquired hydrocephalus can develop at any age due to diseases
manage acute deterioration, and when surgery is not an option or such as tumors and inflammatory disease. Neurological deficits are
not indicated. Acetazolamide, furosemide, or omeprazole are used similar to those in young patients, but if hydrocephalus develops
to decrease CSF formation. Glucocorticoids, such as prednisone, after the cranial sutures have closed, malformation of the skull does
are also commonly used. Although these drugs can provide tempo- not develop.
rary relief, medical therapy does not provide long‐term benefit and
definitive treatment is a surgical procedure to divert CSF, most Diagnostic Evaluation
commonly implantation of a ventriculoperitoneal shunt. The diagnosis of hydrocephalus is based on clinical and imaging
features. Magnetic resonance imaging (MRI) is the best modality
Clinical Features to assess ventricular size and other lesions. Obstructing masses
Based on the age of onset, hydrocephalus can be broadly classified such as tumors, granulomas, and diverticula may be identified,
as pediatric or acquired. Pediatric hydrocephalus is caused by especially on postcontrast images. MRI is more sensitive than
developmental abnormalities and clinical signs are usually apparent computed tomography (CT) in demonstrating small focal lesions,
by several months of age. Toy and brachycephalic dogs are at especially those in the caudal fossa. CT is usually sufficient for
increased risk but the condition occurs sporadically in other breeds follow‐up of previously diagnosed patients and those with an
of dogs and cats. In most cases an obvious site of obstruction is not existing shunt. Ultrasound is practical for assessing ventricular
apparent, but may be due to obstruction at the level of the subarach- size in patients with a persistent fontanelle. Enlarged ventricles
noid space or arachnoid villi, which is difficult to detect. Another are easily seen with any of these techniques, although there is
possibility is intraventricular obstruction during a critical stage of poor correlation between clinical signs and ventricular size.

Current Techniques in Canine and Feline Neurosurgery, First Edition. Edited by Andy Shores and Brigitte A. Brisson.
© 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/shores/neurosurgery

129