Treatment


Conservative treatment

Upon diagnosis, medical treatment should be initiated. Based on previously reported cases [14], this is achieved through the administration of steroids (1 mg/kg/day prednisone administered for 3 weeks) and vitamin A.

Vitamin A supplementation

Since vitamin A deficiency is considered the most consistent underlying cause of this abnormality, supplementing the sick lion with an excessive amount of vitamin A is indicated as the first therapeutic strategy.

Vitamin A supplementation at a dose of 500,000 IU/day injected into the lion’s food for 8 weeks or 2,000 IU/kg body weight injected intra-muscularly (i.m) once a week for 4 week followed by an i.m. dose every other week for 8 week (four additional injections) [3].

Surgical treatment

Is indicated when

  1. The more severe cases where waiting for the medical treatment to exert its effect may risk the lion’s life
  2. When medical treatment failed to improve the clinical signs within two weeks of treatment
  3. When clinical signs were improved but the lion is not back to normal and on follow-up imaging the cerebellum and spinal cord are still compressed due to abnormal thickening of the bones around the caudal fossa.

Surgical decompression, through sub occipital craniectomy, is aimed to to decompress the caudal fossa and relieve the pressure over the cerebellum and spinal cord allowing better drainage of the cerebrospinal fluid hence reducing the intracranial pressure and bring an immediate relieve of the clinical signs.

The following surgical technique was performed with success several times and was described in details by Shamir M et al 2008, and Mc Cain et al [3,12] Surgical procedure

To reduce intracranial pressure and brain volume during bone removal, 1 mg/kg furosemide was administered i.v. followed by slow-rate infusion over 45 min of 0.6 gm/kg mannitol before entering the cranial cavity [15].

  • The lion’s head was elevated and fixed in a special device made of a large, padded cylinder to provide flexion of the neck and head to expose the atlanto–occipital joints and to ensure no additional pressure over the jugular veins.
  • Dorso–median skin incision was made, centered above the atlanto–occipital joint.
  • Muscles of the neck were bluntly dissected at the midline and retracted to expose the caudal aspect of the occipital bone and the atlanto–occipital joint.
  • A highspeed drill was used to remove the thick and abnormally soft occipital bone along preplanned landmarks.
  • Care was taken to avoid the transverse sinus that passed above the thickened tentorium and occipital emissary vein that runs laterally to enter the skull through the mastoid foramen [12].
  • As soon as the bone was removed, the cerebellar vermis and tips of the cerebellar hemispheres on each side protruded out of the caudal fossa.
  • Minor bleeding from the bone was controlled by the application of bone wax. Gel foam and free fat graft were used to cover the exposed nervous tissue prior to routine closure of muscles and skin.

After Surgery

  • 3D CT caudal view of an affected lion after decompression surgery

  • sagital reconstruction of an affected lion after surgery

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Merav Shamir
Rona Nadler

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