Page 983 - Cote clinical veterinary advisor dogs and cats 4th

482 Hydrocephalus

• Autosomal recessive inheritance in Siamese • Ventriculomegaly results from obstruction parainfluenza, canine distemper), nonin-
cats within the ventricular system, overproduction fectious (breed specific, meningoencepha-
VetBooks.ir RISK FACTORS • Congenital ○ Idiopathic: intracranial arachnoidal cysts
of CSF, or insufficient absorption of CSF at
lomyelitis of unknown cause)
the arachnoid villi.
○ Trauma: hydrocephalus ex vacuo occurs
Vitamin A deficiency, toxicosis (cats: griseo-
fulvin during pregnancy), infectious (cats:
cephalic aqueductal stenosis. There is no
panleukopenia, feline infectious peritonitis; ○ Fusion of the rostral colliculi and mesen- with destruction of brain tissue (e.g.,
cerebrovascular accidents)
dogs: parainfluenza), ciliary dyskinesia other active disease process. ○ Toxin exposure: griseofulvin
• Acquired
ASSOCIATED DISORDERS ○ Exposure to teratogenic drugs, chemicals, Initial Database
Small birth size, short gestation periods, high and viral diseases during gestation • CBC, serum biochemistry profile, urinalysis:
stress at birth (dystocia) ○ Obstruction of ventricular system by neo- generally unremarkable for congenital causes
plastic mass, hemorrhage, or inflammation • Serologic titers: to rule out acquired infec-
Clinical Presentation ○ Hydrocephalus also can be a component tious causes, if appropriate
DISEASE FORMS/SUBTYPES of other anomalous disorders (e.g., Chiari • Skull radiography: decreased prominence of
• Congenital: presumably associated with malformation, intracranial arachnoid cyst, normal calvarial convolutions
stenosis of mesencephalic aqueduct and Dandy-Walker syndrome, lissencephaly,
malformation of the mesencephalon cerebellar hypoplasia, ciliary dyskinesia). Advanced or Confirmatory Testing
• Acquired: caused by obstructive insults at • Ultrasonography: through persistent breg-
any age (i.e., infection, trauma, neoplasia) DIAGNOSIS matic fontanelle to visualize enlarged ven-
• Communicating: accumulation of CSF tricles as paired anechoic regions. Enlarged
within the entire ventricular system resulting Diagnostic Overview ventricles are a feature of hydrocephalus, but
from obstruction of CSF outflow pathways Diagnosis is suspected based on the physical not all animals with ventriculomegaly have
(lateral aperture or arachnoid villi) exam and signalment. Confirmation comes from hydrocephalus.
• Obstructive (noncommunicating): ventricular diagnostic imaging (beginning with ultrasound • Cross-sectional imaging: to confirm hydro-
dilation resulting from lesion obstructing and proceeding to CT/MRI if needed) and cephalus and rule out other contributing
CSF flow within the ventricular system procedures assisting in determining underlying disorders and differentials that can mimic
• Subtypes based on location of CSF causes. disease
○ Internal: accumulation of CSF within ○ CT: visualization of lateral ventricles
ventricular system Differential Diagnosis ○ MRI (p. 1132): visualization of the ven-
○ External: accumulation of CSF within the • Hydrocephalus usually produces signs of tricular system and the brain parenchyma
subarachnoid space forebrain dysfunction. (periventricular edema); periventricular
○ Compensatory: CSF accumulates in areas • Encephalopathies hyperintensity indicates interstitial edema
where there is loss of neural parenchyma; ○ Degenerative disorders: storage diseases, • CSF analysis (pp. 1080 and 1323): to rule
also called hydrocephalus ex vacuo leukodystrophies, multisystem atrophy out inflammatory disorders, if appropriate
○ Anomalies (congenital): malformations • Electroencephalography
HISTORY, CHIEF COMPLAINT (e.g., caudal occipital malformation
• Changes in mentation: dullness, obtundation, syndrome, Dandy-Walker syndrome, TREATMENT
disorientation, stupor hydranencephaly)
• Behavioral abnormalities: inability to learn ○ Metabolic: hepatic encephalopathy, Treatment Overview
(e.g., litter box use), loss of housebreaking, organic acid disorders The treatment of hydrocephalus is guided by
compulsive activities, aggression ○ Neoplasia: causes secondary obstructive the underlying cause. Medical therapy offers
• Visual deficits hydrocephalus temporary palliation of clinical signs. Surgical
• Progressive neurologic dysfunction (e.g., ○ Inflammatory: infectious (feline pan- management using shunting procedures may
circling, pacing) leukopenia, feline infectious peritonitis, offer a more permanent remedy.
• Seizures
• Clinical signs may not be apparent.
PHYSICAL EXAM FINDINGS
• Domed-shaped head and persistent fontanelle
are possible.
• Eye position typically will manifest ventral
or ventrolateral strabismus.
• Neurologic exam (p. 1136): mentation
changes, cognitive dysfunction; gait abnor-
malities can manifest as dysmetria, ataxia,
circling, aimless wandering, central blindness,
vestibular dysfunction; seizures
Etiology and Pathophysiology
• Pathologic changes include focal destruc-
tion of the ependymal lining, compromise
of cerebral vasculature, damage to peri-
ventricular white matter, and injury to
neurons.
• Secondary calvarial abnormalities depend HYDROCEPHALUS Magnetic resonance imaging (transverse plane) of a dog with hydrocephalus (left) and
on the stage of ossification at onset of fluid a normal dog for comparison (right). Cerebrospinal fluid appears white in these T2-weighted images. Note the
accumulation. marked dilation of both ventricles in the dog on the left and the normal ventricular volume in the dog on the right.

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