Dandy-Walker-Like Malformation in a Free-Ranging Atlantic Harbour Seal Pup (Phoca vitulina concolor).

An 88.5 cm long, 12.9 kg, 3-week-old stranded male Atlantic harbour seal (Phoca vitulina concolor) presented with cerebellar ataxia, delayed postural reactions, hyperaesthesia and nystagmus. The skull was enlarged and domed. Ultrasound through a persistent fontanelle in the frontal bone revealed hydrocephalus. Magnetic resonance imaging showed diffuse enlargement of the ventricular system, an absent cerebellar vermis, hypertrophy of the choroid plexus of the fourth ventricle and enlargement of the caudal fossa. Throughout rehabilitation, the seal failed to achieve milestones critical for successful release or placement in a managed care facility, including the ability to feed independently and haul out. Three months into rehabilitation it began to regurgitate and staff had difficulty administering food to the seal. The seal was euthanized due to a poor prognosis. Post-mortem examination confirmed a) aplasia of the dorsal cerebellar vermis and hypoplasia of the most dorsal portions of the right and left cerebellar hemispheres, b) severe, diffuse, congenital communicating hydrocephalus, and c) aplasia of the interthalamic adhesion and corpus callosum. This case represents the first report of Dandy-Walker-like malformation (DWLM) in a marine mammal and illustrates the importance of advanced imaging and thorough post-mortem examination in free-ranging pinnipeds that strand with evidence of neurological disease.

A deletion in the VLDLR gene in Eurasier dogs with cerebellar hypoplasia resembling a Dandy-Walker-like malformation (DWLM).

Dandy-Walker-like malformation (DWLM) is the result of aberrant brain development and mainly characterized by cerebellar hypoplasia. DWLM affected dogs display a non-progressive cerebellar ataxia. Several DWLM cases were recently observed in the Eurasier dog breed, which strongly suggested a monogenic autosomal recessive inheritance in this breed. We performed a genome-wide association study (GWAS) with 9 cases and 11 controls and found the best association of DWLM with markers on chromosome 1. Subsequent homozygosity mapping confirmed that all 9 cases were homozygous for a shared haplotype in this region, which delineated a critical interval of 3.35 Mb. We sequenced the genome of an affected Eurasier and compared it with the Boxer reference genome and 47 control genomes of dogs from other breeds. This analysis revealed 4 private non-synonymous variants in the critical interval of the affected Eurasier. We genotyped these variants in additional dogs and found perfect association for only one of these variants, a single base deletion in the VLDLR gene encoding the very low density lipoprotein receptor. This variant, VLDLR:c.1713delC is predicted to cause a frameshift and premature stop codon (p.W572Gfs*10). Variants in the VLDLR gene have been shown to cause congenital cerebellar ataxia and mental retardation in human patients and Vldlr knockout mice also display an ataxia phenotype. Our combined genetic data together with the functional knowledge on the VLDLR gene from other species thus strongly suggest that VLDLR:c.1713delC is indeed causing DWLM in Eurasier dogs.

Magnetic resonance imaging diagnosis of Dandy-Walker-like syndrome in a wire-haired miniature dachshund.

A 12-week-old female Wire-haired miniature dachshund presented with non-progressive ataxia and hypermetria. Due to the animal's clinical history and symptoms, cerebellar malformations were suspected. Computed tomography (CT) and magnetic resonance imaging (MRI) detected bilateral ventriculomegaly, dorsal displacement of the cerebellar tentorium, a defect in the cerebellar tentorium and a large fluid-filled cystic structure that occupied the regions where the cerebellar vermis and occipital lobes are normally located. The abovementioned cystic structure and the defect in the cerebellar tentorium were comparable to those seen in humans with Dandy-Walker syndrome. However, the presence of the cystic structure in the occipital lobe region was unique to the present case. During necropsy, the MRI findings were confirmed, but the etiology of the condition was not determined.

[A case of a congenital high-grade hydrocephalus internus and Dandy-Walker syndrome in a black and white German Holstein calf]. / Ein Fall von angeborenem hochgradigen Hydrocephalus internus und Dandy-Walker-Syndrom bei einem schwarzbunten Kalb der Rasse Deutsche Holsteins.

A black and white female German Holstein calf showed a highly deformed cranium. The animal was not able to stand. Further findings were bilateral strabismus divergens and negative pupillary light reflexes. Magnetic resonance imaging and pathological-anatomical examination showed that the cerebrum was replaced to a high degree by the ventricle system filled with 1.5 liters of cerebrospinal fluid. The hemispheres of the cerebellum were ruptured by the dilated fourth ventricle. In addition, the vermis and pons were missing and fluid accumulation in the subarachnoidal space extending up to the first spinal cord segments was visible. Inbreeding was not detected in the 3-generation-pedigree. No other affected calves from the same parents were known at the farm. Chromosomal abnormalities could not be detected after examination of 30 metaphase spreads using a light microscope. Infections and parasitic diseases could be ruled out for this anomaly. Very rare defect alleles might have been involved in the development of these inborn defects.

Ultrasonographic appearance of Dandy Walker-like Syndrome in a Boston Terrier.

Congenital cerebellar disorders can be caused by in utero or neonatal infections, genetic aberrations causing malformations, and neurodegenerative processes. Most congenital cerebellar disorders are diagnosed definitively with histopathology. However, antemortem diagnosis of cerebellar malformations can be made by imaging the brain. This paper describes the antemortem appearance of a congenital cerebellar malformation in a Boston Terrier puppy on ultrasound images. This appearance was compared with the postmortem findings that were comparable to Dandy Walker Syndrome in humans. A previous report of this syndrome in Boston Terriers suggests the problem may be inherited in this breed.

Hydromyelia in the dog.

Hydromyelia is a dilation of the spinal cord central canal. In man this may be due to congenital malformations such as Dandy-Walker syndrome and Chiari malformations or may be acquired as result of infection, trauma or neoplasia. In dogs hydromyelia may be accidentally diagnosed during routine cisterna magna myelography. Hydromyelia, and its possible etiology, may be confirmed by means of computed tomography or magnetic resonance imaging. Three dogs with hydromyelia due to differing etiologies are described.

Dandy-Walker malformation in two calves.

Two calves with unusual malformations of the skull and brain are described. Both calves showed doming of the posterior skull due to enlargement of the posterior fossa and cyst-like dilatation of the fourth ventricle. The cystic dilatation of the fourth ventricle formed a meningocoele in one calf. Aplasia of the cerebellar vermis was present in both calves. One calf showed agenesis of the corpus callosum. These features are consistent with the Dandy-Walker malformation of man.