Case of the month August 2006 Cavalier King Charles Spaniel, m, 3.5 y
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Case of the month
August 2006
Cavalier King Charles Spaniel, m, 3.5 y
Episodes of suddenly occurring onsets of forelimb and/or hind limb lameness. During episodes crying out of pain. Frequency of episodes increasing. Scratches his head.
History
Dog was referred to the Neurology division of the Vetsuisse Faculty Berne because of
Results of neurologic examination
• Manipulation of neck leads to withdrawal of right forelimb; biting into paw; similar reactions of hind limbs
• Paraesthesia• Head scratching, episodes of agitation, then
suddenly back to normal • All reflexes normal
LocalisationBrainstem, medulla oblongata, cervical spine, inner ear
FSE T2 transverse
dorsal
right
Level of middle ear
right
Normal for comparison
dorsal
Level of middle ear (M)
MM
MRI of head and neck
Plain
dorsal
right
Level of middle ear
MRI of head and neck
right
Contrast enhanced
dorsal
Level of middle ear
FE 3D T1 transverse
T2 mid sagittal
dorsal
rostral
MRI of head and neck
C cerebellum, arrows: second cervical vertebra
C
Findings
Both middle ears („bullae“) are filled with hyperintense material in T2 (arrows; compare with normal) and T1. Neither the material nor the epithelial lining of the bullae takes up contrast.
A small part of the cerebellum is herniated caudally to the dorsal border of the foramen magnum (arrow); the most cranial part of the spinal cord is incarcerated between the dens axis (D) and the dorsal foramen magnum.
The spinal cord shows a severely widened and deformed central canal (arrowheads).
D
Findings
Summary
Fluid filled middle ears on both sides without signs of acute middle ear inflammation. Cerebellar herniation caudally through the foramen magnum, incarceration of the most cranial spinal cord and severe hydrosyringomyelia (dilatation of the central canal) of the cervical spinal cord.
Interpretation
These findings are consistent with Chiari malformation type 1.
Arnold Chiari malformations are developmental disorders which are overrepresented in Cavalier King Charles Spaniels. They can be clinically silent or cause severe neurological deficits. Their main feature is the caudal displacement of the cerebellum, resulting in „crowding“ of the foramen magnum and disruption of normal cerebrospinal fluid (CSF)-flow leading to hydrosyringomyelia. Associated are increased intracranial pressure and malformation of the foramen magnum. Fluid filled middle ears are common findings in this breed, but not related to the Arnold Chiari malformation.
Comment
For this condition a hereditary component is suspected, and dogs with that malformation should be excluded from breeding. MRI provides a safe and non-invasive method for in vivo diagnosis of this disorder.
Further information on this condition is available on: http://www.ivis.org/advances/Vite/braund16/chapter.asp?LA=1
Comment
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