Head Tilt – Rabbit

Also known as Torticollis

The most common neurological disorder of rabbits is head tilt or torticollis

Aetiology

Peripheral vestibular disease

Peripheral vestibular diseases corresponds to an extension of otitis externa or from the nasal cavity to the middle or inner ear via the Eustachian tube, the trigeminal nerve or by a haematogenous route so it is often associated with respiratory infections.

The causative organisms include P. multocida, Staphylococcus spp., Bordetella bronchiseptica, E. coli, Pseudomonas aeruginosa. Psoroptiasis should also be considered.

Treatment includes antibiotics for Pasteurella (also see The Pasteurellar Syndrome) and/or acaricides for psoroptiasis (see chapter on skin disorders).

Various pharmacotherapeutic approaches have been suggested to alleviate the clinical signs:

• Meclozine (Sea-Legs®; SSL International) PO q6–8hrs is suggested to control spinning of affected rabbits (Saunders 2002; Keeble 2006).
• Prochlorperazine (Stemetil®; Distriphar) – PO q8-12hr – oral suspension. If the case is so bad that you can’t manage oral medication, I suppose it might be worth trying a SC dose but the outer pack is 10 ampoules of 12.5mg each and you have the Cascade to consider)
• Personally I’d try cinnarizine (Stugeron®; Janssen Cilag) – I found it useful in dogs with head tilt or idiopathic trigeminal neuropathy so it might help to stabilise a rabbit a bit during the early stages of a head tilt disorder – untested in this species – you have been warned!

Organisms causative of central vestibular or cerebellar disease

These include the bacteria listed above as causing peripheral vestibular disease (with the addition of Listeria monocytogenes)and also protozoan diseases (eg. Encephalitozoon cuniculi and Toxoplasma gondii). Encephalitozoon is not found in the inner ear tissue, only in the CNS where it causes a non-suppurative meningitis and a granulomatous encephalitis, sometimes accompanied by perivascular infiltration with lymphocytes and plasma cells. All areas of the brain are affected.

E. cuniculi may yield biochemical test results indicative of renal disorder and positive serology for E. cuniculi antibodies. Note that E. cuniculi also causes ophthalmic lesions (capsular rupture, cataract development and phacoclastic uveitis).

Treatment of E. cuniculi is described here. For treatment of toxoplasmosis consider sulphonamides and be aware that clindamycin is extremely toxic in this species.

Miscellaneous causes of head tilt in rabbits

Cerebral larva migrans (Baylisascaris procyonis) has also been incriminated. Neoplasia has been diagnosed on MRI or CT scans. Cerebrovascular accidents may also be diagnosed on MRI and propentofylline or nicergoline are suggested as treatments. Another possible cause is trauma, including bites to the back of the neck: supportive treatment should rely on antibiosis and analgesics.

Cerebral mycoses are unlikely to be encountered in the UK. I’d try itraconazole but I would be very dubious of success, given the time take from initial infection to onset of signs and the slow build up of itraconazole to therapeutically effective plasma levels.

Toxicoses:

• Lead – house rabbits which nibble wires etc. Signs include depression lethargy inappetance and “subtle neurologic changes” (Hillyer 1994). Calcium EDTA: q6hrs (Richardson 2000). Saunders (2002) suggests metoclopramide or cisapride (if it ever becomes available), to promote gastrointestinal motility and decreasing the absorption of the heavy metal.
• Woolly milk pod contamination of hay in the USA.

Clinical signs of central and peripheral vestibular disease

Differentiate between central (eg. Encephalitoonosis) and peripheral (eg. Pasteurellosis) vestibular disease in rabbits (Harcourt Brown 2002). Both show:

• Loss of balance
• Head tilt
• Falling
• Horizontal nystagmus
• Rotary nystagmus
• Ventrolateral strabismus
• Signs shown in central but not in peripheral vestibular disease
• Rolling
• Vertical nystagmus
• Positional nystagmus
• Signs shown sometimes in central but never in peripheral vestibular disease
  • Intention tremor (cerebellar)
  • Hemiparesis with ipsilateral postural reaction deficits
• Mentation
  • Central vestibular cases are possibly depressed whereas peripheral cases are probably not

Diagnostics to differentiate between Encephalitoonosis and Pasteurellosis

• Radiographic changes seen in tympanic bulla in pasteurellosis
• Serology
• Haematology – neutrophilia and a shift to the left might indicate bacterial infection

Therapeutic approach to head tilt in rabbits

• Oxytetracycline IM and low dose + corticosteroid IM + benzimidazoles
• Diazepam IM
• Meclozine PO q6–8hrs
• Prochlorperazine PO q8-12hr – oral suspension.
• Cinnarizine q 12–24 h

Corticosteroids in rabbits

• Consider absorption from topical applications
• Compromisation of premunity
• In anorexia, mobilizes free fatty acids from adipose tissue => hepatic lipidosis
• Increased populations of intestinal coliforms
• Ratio of aerobes to anaerobes alters
• Reserve for acute cases

Note: Chronic pruritic seborroeic otitis is usually associated with yeasts (Candida sp.) whereas purulent otitis, especially where the discharge is tacky and sticky, may show E. coli and Pseudomonas sp on culture.

References

• Hillyer, E. V. (1994) Pet Rabbits. Veterinary Clinics of North America: Small Animal Practice. 24 (1) 25-65.
• Keeble, E. (2006) Nervous and Musculoskeletal Disorders in BSAVA Manual of Rabbit Medicine and Surgery eds Meredith A and Flecknell P, 2nd Edition 2006, published by BSAVA Quedgley Glocs
• Richardson, V. (2000) Rabbits: Health, husbandry and disease. Blackwell Science, Oxford
• Saunders, R. (2002) Understanding Head Tilt in Rabbits "New Directions": Small Animal Eyes and Ears (from the publishers of Veterinary Times) Issue 1, Volume 1, Feb 2002 pages 4-5