Dandy-Walker syndrome

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Dandy-Walker syndrome is a rare neurological disease of dogs.

Dandy-Walker syndrome refers to complex heterogeneous developmental anomaly characterized by the morphological triad of aplasia or hypoplasia of the cerebellar vermis (especially the caudal portion), cyst-like dilatation of the fourth ventricle, and hydrocephalus[1]. Dandy-Walker syndrome is believed to be a disorder of fusion of dorsal midline structures of the primitive neural tube. Failure of development of the midline portion of the cerebellum forms the basis of this syndrome with subsequent enlargement of the posterior fossa, abnormally high placement of the tentorium, and elevation of the transverse sinuses. The syndrome may also be associated with syringomyelia and agenesis of the corpus callosum.

A similar syndrome has been reported in several breeds of dogs including Beagle, Australian Silky Terrier, Chow Chow, Tervuren, Boston Terrier, Briard, Labrador Retriever, Bull Terrier, Weimaraner, and Dachshund[2][3]. Cases are characterized by cerebellar vermian aplasia or hypoplasia, often associated with a fluid-filled, cyst-like structure in continuity with a dilated fourth ventricle that fills the posterior fossa. A communicating hydrocephalus is frequently present.

Pathology

The pyramis, uvula, and nodulus cerebellar lobules were commonly involved in several reports involving dogs. Additionally, portions of the cerebellar hemispheres and flocculus can be affected. Microscopic changes may include focal or scattered Purkinje cell chromatolysis and atrophy, indistinct deep cerebellar nuclei, scattered axonal spheroids, and reduction of granule cells in the cerebellar cortex. Retrograde transynaptic neuronal degeneration, such as chromatolysis or vacuolation of neurons, may be noted in brainstem nuclei that project to the cerebellum, including olivary, lateral reticular, lateral cuneate and vestibular nuclei. The lateral apertures through which the fourth ventricle communicates with the subarachnoid space appear to be microscopically normal in dogs. The wall of the posterior fossa cyst may be lined by piaarachnoid, neuropil, and an inner layer of flattened ependymal cells [64] or by ependymal cells alone [82]. Hydromyelia is not usually a feature but has been reported in two adult dogs[4].

Clinical signs

Clinical signs of ataxia, dysmetria, absent menace response, and intention tremors reflect a cerebellar syndrome. In addition, some animals with flocculonodular lobe lesions may show a vestibular syndrome, such as head tilt, nystagmus, ventromedial strabismus, circling, and falling. Seizures, behavioral abnormalities and visual impairment may be seen in animals with hydrocephalus[5]. A bunny-hopping gait was observed in one 12 week old Beagle. Clinical signs tend to be nonprogressive and may be seen in young animals as early as 2 weeks of age or may be delayed until 3 or 4 months of age. The condition has also been reported in adult dogs: a 4 year old Cavalier King Charles Spaniel and a 2.5 year old Maltese Poodle with signs of intermittent pain and paresis/hypermetria, respectively.

Diagnosis

Analysis of cerebrospinal fluid is normal. Radiographic studies may reveal a very thin and dome-shaped calvarium with a smooth ground glass" appearance, suggestive of hydrocephalus. Scalloping of the inner table of occipital bone was observed in one dog. A dilated ventricular system and cystic dilatation of the fourth ventricle can be identified using MRI[6] or cisternography. Hydromyelia was diagnosed in two adult dogs using myelography and MRI. Prognosis depends on severity of clinical signs.

Treatment

If the signs are mild, prognosis for longevity and quality of life may be good, especially since signs tend to be non-progressive.

References

  1. Golden JA, Bonnemann CG. (1999) Developmental structural disorders. In: Goetz CG, Pappert EJ, eds. Textbook of Clinical Neurology. Philadelphia: WB Saunders Co, pp:510-537
  2. Pass DA, Howell JM, Thompson RR. (1981) Cerebellar malformation in two dogs and a sheep. Vet Pathol 18:405-407
  3. Schmid V, Lang J, Wolf M. (1992) Dandy-Walker-like syndrome in four dogs: cisternography as a diagnostic aid. J Am Anim Hosp Assoc 28:355-360
  4. Kirberger RM, Jacobson LS, Davies JV, et al (1997) Hydromyelia in the dog. Vet Radiol Ultrasound 38:30-38
  5. Regnier AM, de Lahitte MJD, Delisle MB, et al (1993) Dandy-Walker syndrome in a kitten. J Am Anim Hosp Assoc '29:514-518
  6. Schmid V, Lang J, Wolf M. (1992) Dandy-Walker-like syndrome in four dogs: cisternography as a diagnostic aid. J Am Anim Hosp Assoc 28:355-360