Head Tilt and Other Neurological Disease in the House Rabbit

by Susan A. Brown, DVM - Midwest Bird and Exotic Animal Hospital Westchester, IL 60154

Head tilts in rabbits are seen with some frequency and can be caused by a variety of diseases. Another common name for head tilt is “wry neck” and the “scientific” name is vestibular disease (which actually can include other signs along with the head tilt). Rabbits exhibiting a head tilt also experience a loss of balance causing falling over to one side or circling to one side. In this lecture we will look at some of the causes and treatments of diseases that cause a tilted head in the rabbit as well as some of the diseases that can cause other signs of weakness and loss of the ability of the rabbit to move normally. The lecture notes will be presented in an outline format to allow you to take notes as we go along.

And off we go!!!

ANATOMY

First we need to understand the anatomy and function of some vital areas in the rabbit in order to understand how this condition comes about.

I. External ear

A. Easily visible - should be inspected weekly

B. May be original site of disease

C. Disease in this area can cause head shaking, drooping ear and pain

II. Middle ear

A. Includes the eardrum (tympanic membrane), eustachian tube, 3 auditory ossicles (bones) and tympanic nerve (branch of the facial nerve CN VII). Protected by the tympanic bulla (bony shell)

B. May fill with fluid or pus - may or may not cause changes in the ear drum appearance

C. Disease can come from external ear or through eustachian tube from the pharynx or through the blood

D. Disease in this area can cause the same signs as with external ear along with deafness.

E. If facial nerve is damaged - drooping lip, drooling, decreased or no blink reflex and drooping ear. If damage to nerves III, IV or VI then will have Horner’s Syndrome (drooping lip, sunken eye, relaxed third eyelid). In some cases the eye becomes very dry.

III. Inner ear

A. Includes cochlea, vestibule and semicircular canals and innervated by the vestibulocochlear nerve. Controls balance and hearing.

B. Disease can come from middle ear or through the blood

C. Signs of disease include deafness, head tilt, loss of balance, circling and rolling, horizontal or rotary nystagmus (eye “flipping” or rolling) which is spontaneous and occurs independent of head position.. Proprioception and postural reactions are normal.

D. Nausea may occur in rabbits ? Possibly cause tooth grinding and excessive salivation?

IV. Nerves

A. Vestibulocochlear nerve (CN VIII) - Originates in the brain

• a. Difficult to detect deafness in a rabbit, particularly if only on one side.
  b. Try training the rabbit to a specific sound at feeding to be able to detect deafness later in life.
1. Vestibular branch controls balance and normal head posture by using sensors in the semicircular canals. It has connections with Cranial nerves (CN) III, IV and VI, which control proper eye movements.
2. Cochlear branch controls hearing through the cochlea

B. Facial nerve

1. Many branches, but some go through area of ear
2. Controls tongue, glandular cells of nasal cavity, mandibular and sublingual salivary glands and lacrimal (tear) gland. It also controls the movement of the lips, eyelids and ears.

V. Brain

A. Brain oversees all functions in the body. Disease of the brain can result in a wide variety of signs.

B. Brain stem - is the location of the vestibular nuclei which is related to the vestibular nerve and is the central control over balance

C. Disease of the brain stem causes head tilt, circling, rolling, nystagmus (but only when the animal’s head position is moved and it varies with head position), delayed or absent proprioception and loss of postural reactions.

VI. Spinal cord

A. “Powered” by the brain and contains the base of nerves that control every function in the body.

B. Sensory and motor nerve function

C. Damage only to spinal cord is not associated with head tilt

D. Damage to spinal cord depends on the level of the lesion and may be unilateral or bilateral including loss of function of limbs, complete paralysis, loss of bladder and bowel control, loss of breathing control, etc.

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DIFFERENTIATING BRAIN STEM FROM INNER EAR DISEASE*

Sign Inner Ear Brain Stem Head tilt Present Present Circling Present Present Falling, rolling Present Present Nystagmus Usually spontaneous and Usually not spontaneous - found does not vary with head with changes in head position position Conscious proprioception Normal Delayed or absent Horner’s syndrome May be present Absent Gait changes Mild to severe ataxia Ataxia and weakness Postural reactions (hopping, Normal if examined slowly Weak or absent hemiwalking, etc)

*Adapted from Saunders Manual of Small Animal Practice, SJ Birchard, RG Sherding editors, W.B. Saunders Company, Philadelphia, PA, 1994. DISEASES AND TREATMENT

I. OTITIS MEDIA OR INTERNA (Inflammation of the middle or inner ear)

A. Probably the most common cause of head tilt in the rabbit

B. Causes

1. Infectious - a variety of bacteria, NOT just Pasteurella a. Bacteria can spread from upper respiratory system, through the eustachian tube, from the external ear canal and through the blood from infections elsewhere in the body.
2. Parasitic a. Severe ear mite infestation causing damage to ear drum and subsequent disease
3. Trauma a. Blow to the ear or head causing bleeding
4. Foreign body a. Plant material or other object puncturing the ear drum
5. Neoplasia (cancer)

C. Signs

• a. Pain on affected side, head shaking, head rubbing or scratching excessively at the ear
  b. If damage to cranial nerves see any combination of drooling, reduced or no blink reflex, dry eye, drooping lips or Horner’s syndrome
1. If only middle ear
2. If inner ear a. Head tilt, circling, rolling and nystagmus,
3. Although unusual, either condition can result in loss of appetite if there is a sufficient pain in involved

D. Diagnosis

1. History and physical examination including neurological and exam of ear with an otoscope a. In a few cases there may be changes in the appearance of the ear drum (inflamed, bulging, ruptured, etc.)
2. Radiograph of the head to look for thickening of tympanic bulla or pus in the area (NEITHER have to be present)

E. Treatment (for either condition)

1. Treat external ear canal infection if present by flushing out debris and culture USE SALINE ONLY TO FLUSH EAR IF THE EAR DRUM IS RUPTURED
2. Culture material in middle ear if possible (but difficult and often nothing there)
3. Treat with antibiotics for several weeks to months
4. May use corticosteroids for one to three days to help reduce inflammation and damage to nerves - THIS TREATMENT IS STILL CONTROVERSIAL - follow your veterinarian’s instructions
5. Perform surgery if necessary to remove debris from the middle ear
6. Generally DO NOT use topical medications in the ear canal unless there is serious external ear infection and the ear drum is INTACT. Ivermectin can be used for ear mites by injection **There are several products that if used topically in the ear canal of a rabbit with a ruptured ear drum can be ototoxic and produce deafness, head tilt and loss of balance (or make the existing condition worse). These include: Iodine products, chloramphenicol, gentamicin, neomycin and chlorhexidine (Nolvasan)
7. Good nursing care for many weeks to months (see section on CARE OF THE DEBILITATED RABBIT)
8. May consider acupuncture.
9. Antinausea drugs may or may not be useful - controversial

F. Prognosis

1. If the rabbit maintains an active and alert attitude throughout and continues to eat on its own, the prognosis is guarded to good.
2. If the rabbit becomes weak, lethargic and loses the appetite or function of the limbs, the prognosis is poor to grave because it it likely the disease is affecting deeper areas.
3. Always assume that the condition will be WORSE before it gets BETTER no matter what the treatment is. The first three weeks are some of the worst and usually by the end of three weeks one can tell the worst it will be.
4. Some rabbits return to completely normal in weeks to months and some rabbits always have a head tilt that may be accentuated when the pet is excited.
5. This disease can reoccur months to years after the first experience

II. TRAUMA

A. Occasionally a cause of head tilt in the rabbit

B. Signs - same as for otitis and for brain stem lesions plus there may be additional signs if other areas of the brain are affected.

C. Diagnosis

1. History of trauma
2. Radiographic evidence of cranial fractures
3. Blood in the ear canal

D. Treatment - same as for otitis but without the antibiotics usually, corticosteroids may be used for a longer period of time

E. Prognosis - same as for otitis following the same signs, but will likely have a more rapid recovery period.

III. PARASITIC

A. Encephalitozoon cuniculi (Nosema)

• a. Small one celled-protozoa commonly infecting the rabbit population (as well as other animals and rarely in humans)
  b. Passed from infected animals in the urine then passes through the kidneys and infective cells are shed in the urine
  c. Spores in the body stay there for life and usually cause no problem (up to 80% of some normal rabbit populations are positive for this parasite) but can at any time spread to other tissues including the brain and spinal cord.
  a. This is difficult as this disease can mimic other diseases
  b. Blood serology can be done but is only minimally helpful
  c. Tentatively diagnosed on signs and rule out of other disease (particularly otitis interna)
  a. There is no currently available known effective treatment for this disease.
  b. Some drugs used in the lab, but not yet on live animals may show promise.
  c. No drug will reduce damage already done, but hope it to prevent further damage.
  d. Corticosteroids are used to minimize nerve damage
  e. Supportive care
  a. Very guarded in these cases as we do not know if the disease will “flare up” again.
  b. Some rabbits have periods of recovery while others continually have degenerative signs over time.
1. Cause
2. Signs a. Signs are very variable depending on the area of the brain or spinal cord affected and can include any combination of the following: unilateral or bilateral facial paralysis, weakness or paralysis in one or more limbs, head tilt, circling, rolling, nystagmus, loss of appetite, behavior changes, depression, seizures and sudden death.
3. Diagnosis
4. Treatment
5. Prognosis

B. Baylisascaris procyonis (Raccoon roundworm larva migrans)

• a. Adult worms found in raccoons in many areas of the country
  b. When non-host animal ingests the eggs passed in raccoon feces, the hatching larva travels to a variety of places such as liver, eyes, spinal cord and brain. The larva is large and causes a great deal of tissue damage and subsequent death when it invades these areas.
  c.. This parasite can affect humans as well as a wide variety of animals including most domestic pets.
  a. As with E. cuniculi, this is very difficult to diagnose while the animal is alive
  b. History may suggest exposure to outdoors or feed contaminated by raccoon feces
  c. Other diseases will be ruled out
1. Cause
2. Signs a. Similar to those seen with E. cuniculi with the possible addition of abdominal pain and blindness.
3. Diagnosis
4. Treatment & Prognosis - same as for E. cuniculi

IV. CEREBROVASCULAR DISEASE

A. Arteriosclerosis (”Hardening of the arteries”)

1. Rare in the rabbit to be caused by fat
2. Mineralization of the blood vessels reported likely due to dietary imbalances - mineralized vessels can be seen on radiograph

B. Infectious

1. Abscesses in the brain of rabbits is rare, but has been seen Signs would be varied depending on the area of the brain that was affected

C. Cerebrovascular accident (”Stroke”)

1. Cause - Brain tissue dies due a lack of blood supply caused by any of the following: embolism, blood clot or hemorrhage
2. Signs - varied, depending on the area of the brain affected
3. Diagnosis - in humans can be done with CT scans and brain dye studies - expensive and difficult to find facilities for rabbits to do this Rule out other disease.
4. Treatment - Corticosteroids, possibly antibiotics and supportive care. Use of anticoagulants may be dangerous

D. Neoplasia - cancerous growths in the brain can cause pressure and damage to the vascular system. This condition is rare in rabbits

V. TOXINS

A. Rabbits can ingest toxins that might cause a variety of signs including head tilt, loss of balance, weakness, seizures and sudden death.

B. Toxins to consider are: lead or zinc (paint, cages, costume jewelry, imported pottery, curtain weights, x-ray proof film bags, etc.), insecticides (even some labeled “safe” for rabbits), plants (including mushrooms), carbon monoxide and other household materials.

C. Diagnosis is based on the history and diagnostic tests such as x-rays, blood work and urinalysis.

D. Treatment is based on the toxin involved.

VI. MISCELLANEOUS CAUSES OF WEAKNESS OR NEUROLOGICAL DISEASE IN THE RABBIT

A. Spinal disease - fractures, tumors, parasitic, degenerative, intervertebral disc disease, spondylosis, infectious

B. Metabolic

1. Nutritional - hypo or hyper vitaminosis A, hypovitaminosis B and/or E and low amounts of selenium or copper, etc.
2. Hyperthermia- overheating- rabbits are very sensitive to high environmental temperatures and humidity. They MUST be protected in the summer time. They prefer a temperature 75 F or lower.
3. Endocrine - Imbalance of hormones from the thyroid, pancreas, or adrenal. None of these diseases are well documented in the house rabbit
4. Liver disease - brain is “poisoned” by accumulation of toxic products not being removed from the blood by the malfunctioning liver. High blood ammonia is particularly toxic

VII. CARE OF THE DEBILITATED RABBIT

A. MUST make a LONG TERM commitment to the care of the rabbit. None of these diseases are going to be “quick cures”. Many will take weeks to MONTHS to see any positive results.

B. Problems to watch for:

1. Decubital ulcers (”bed sores” from sitting in one place too long or from soiling by stool or urine) Solution: Keep pet on soft absorbent bedding and move positions often. Use protective creams or ointments and bandaging as necessary. Bath anal area as needed and dry thoroughly after the bath
2. Damage to eye(s) when rabbit is falling or rolling Solution: provide cage padding - cover wire floors and walls, use eye ointments as needed to protect eye and treat dryness. Remove toys or items that the toe nails could get caught in - keep the nails trimmed - experiment with using smaller cage or exercise areas until the pet is more stable.
3. Joints become stiff or muscles atrophy. Solution: You will not be able to counteract all of the damage because if there is no nerve innervation to the area, the tissue will eventually contract and become hard and useless. However, physical therapy several times daily for a few minutes can be very helpful. Gently flex and extend the joints at least 20 times at a session. In addition massaging the muscles prior to stretching helps to “warm them up” and loosen them.
4. Handling - can be stressful to the pet especially if there is a loss of balance Solution: Short handling sessions and minimal handling until the pet adjusts to the condition. Many pets over time actually get calmer when certain people handle.
5. Cecotropes - some rabbits cannot reach the anus to eat the cecotropes which are necessary for a healthy diet Solution: You will recognize these vitamin rich droppings because of their shiny mucous coat, stronger smell and unusual shape. Collect these whenever they appear and place them in or near the food area. Most rabbits will eat them on their own. Many rabbits learn to find them on their own in the cage. This is another reason not to have a wire cage floor which will allow the cecotropes to drop out of the rabbit’s reach.
6. Food and water containers. Solution: Experiment with what is most comfortable for your pet. It might be necessary to attach these containers to the side of the cage so the rabbit doesn’t keep pushing them around. Some rabbits can no longer use water bottles, so provide a bowl with shallow water. It may be necessary to elevate or use wider mouthed bowls to make feeding easier.
7. The ridicule of family and friends - hopefully this doesn’t happen to you, but if it does, be assured that you are providing the best possible home for your pet. Solution: Tell them they don’t know what they are missing by having a close connection with an animal that needs special assistance. If you are in doubt about whether or not you are doing the right thing and whether or not your pet is suffering, keep in mind some signs to look - pain in the rabbit can be exhibited in a number of ways, but some of the more common ones are: not eating, not willing to move (even the partially paralyzed bunnies will still try to move), sitting with eyes half closed all the time, hunched whenever it is sitting, extreme lethargy. Work with your veterinarian and have him or her tell you what is happening medically and then do carefully observations of your pet so you can see what is going on “spiritually”.