Back

HYDROCEPHALUS

Note for Pet Owners:

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Topics on this Page:


Description
Hydrocephalus literally means water (hydro-) on the brain (cepahlus). The term is used in medicine and veterinary medicine to describe a pathological condition in which fluid accumulates in the brain.


Cause
Th
ere are 3 basic ways in which fluid can accumulate in the brain :

  • There is an increased production of fluid within the brain. This can occur if a papilloma form in the choroid plexus. This is rare in dogs, but has been reported to occur in Bull Mastiffs with inherited ataxia.
  • Normal fluid absorption from the brain (across the meninges) is impaired. This may occur following inflammation of the meninges (meningitis) or a hemorrhage in the brain (subarachnoid hemorrhage) and this condition is called communicating hydrocephalus.
  • Normal flow of cerebrospinal fluid (CSF) in the brain is obstructed - most frequently this occurs at the level of the cerebral aquaduct, or the lateral foramina of the 4th ventricle of the brain.. This condition is called non-communicating or obstructive hydrocephalus and it may be present at birth (congenital) such as stenosis of the aqueduct, or acquired later in life for example due to infections, tumours or space-occupying hemorrhages (hematomas). This is the most common form of hydrocephalus seen in Toy breeds of dog.

Breed Occurrence
Hydrocephalus is most often seen in Toy breeds of dog especially the :

  • Chihuahua
  • Maltese Terrier
  • Pomeranian
  • Yorkshire Terrier

but it is also seen in brachycephalic dogs such as the : 

 and also in the Beagle, Bull Mastiff, Lhasa Apso and Poodle. The condition is also seen in other species eg cats. Hydrocephalus  may be genetically inherited in breeds with an increased risk.


Signs

The most obvious sign of  hydrocephalus is an enlarged "domed" skull and the spaces between the bones of the skull remain open , as does the fontanel . Progressive neurological signs may not occur in all animals with hydrocephalus, when they do occur they take the form of :

  • Seizures (fits)
  • Depression and dullness
  • Blindness
  • Paresis (limb weakness)
  • Incoordination
  • Strabismus (squinting) - ventrally and laterally.
  • Oedema of the optic nerve (called papillodema) - can be seen on ophthalmoscopic examination of the optic disc.

Untreated hydrocephalus is usually progressive and results in death, but some Toy breed dogs (especially Chihuahuas) can survive without showing clinical signs.


Complications
Rapid removal of CSF in these patients can cause a subdural hemorrhage if the intraventricular pressure suddenly drops, so care is needed when performing corrective drainage surgery or when taking CSF for examination to screen for  meningitis.


Diagnosis
Diagnosis can often be made on clinical signs and physical appearance. It is confirmed by :

  • Radiography with contrast media (eg air ventriculogram) - less satisfactory than new imaging techniques
  • Computerised tomography (CT) scan
  • Magnetic Resonance Imaging (MRI)
  • Ultrasound - if the fontanel is open

All reveal thinning of the bony cortex skull and greatly dilated and enlarged ventricles in the brain.


Treatment
Medical treatments that have been used  include :

  • Corticosteriods - reduce CSF production and reduce any inflammatory reaction
  • Diuretics - to remove fluids by increasing urinary fluid losses
  • Other osmotic agents 

Surgery :

  • Excision of choroid plexus papilloma - rare
  • Excision of a tumour causing obstruction to drainage of CSF
  • Insertion of a tube to drain excess fluid off the brain eg ventriculoatrial and ventriculoperitoneal shunts. These  techniques are more difficult in congenital hydrocephalus and blockage of the drainage tube is a complication once it is in situ.

Damage caused to then brain by the build-up in pressure is permanent and cannot be reversed.


Prognosis
Guarded for all patients,. Acquired hydrocephalus carries the best prognosis for a cur, if an underlying cause can be identified and removed before major brain damage is caused ....eg a localised benign tumour may be removed in it's entirety. 


Long term problems

Permanent loss of brain function due to pressure necrosis.

 

Updated October 2013