Dystocia due to congenital hydrocephalus in a miniature Dachshund

Congenital hydrocephalus (CH) is an active distension of the ventricular system that develops because of either an interruption of cerebrospinal fluid (CSF) flow or absorption. Chihuahua, Pomeranian, Pug, Pekingese, English Bulldog, Lhasa Apso, Yorkshire, Boston, and Maltese Terrier breeds are predisposed to CH. 1 Although Dachshunds have a relatively low frequency of congenital defects compared to other breeds, 2 CH has been previously reported. 3 However, there have been no published reports of CH resulting in dystocia in this breed. An 8 year old multiparous miniature Dachshund presented with a dystocia persisting for > 8 hours. The bitch was clinically stable on physical examination and a digital vaginal examination revealed no fetal parts. Transabdominal ultrasonography of uterus revealed 4 fetuses with heart rates between 150 - 250 bpm. A catheter was placed in the right cephalic vein and the bitch was anesthetized with propofol. Anesthesia was maintained with sevoflurane. A routine hysterotomy was performed and all 4 fetuses were delivered alive, including a fetus with a large, domeshaped head that was lodged in the cranial vagina. No other congenital defects were present during gross postnatal examination of pups. Puppies were followed to 9 weeks of age. The pup with the CH developed normally and displayed no neurologic signs other than a consistent lack of menace reflex. Transfontanelle ultrasonography at 4 weeks of age revealed the lateral ventricles were greatly distended with anechoic fluid and lined by a thin wall of cortical tissue. At 9 weeks of age, the pup (2 kg) began acutely and inconsolably crying and began circling with head pressing. Euthanasia was performed and necropsy findings revealed 5 open fontanelles, occipital dysplasia, and symmetrical ventriculomegaly with periventricular cortical atrophy. Prior to ossification of the cranial sutures, CH may cause abnormalities of skull development such as a thinning of the bone structure, a dome-shaped appearance to the head, and/or persistent fontanelles. 1 In the current case, each ventricle contained approximately 10 ml of cerebrospinal fluid. Concurrent congenital abnormalities of the brain (e.g. intracranial arachnoid cyst, Dandy-Walker syndrome, Chiari-like malformation) without CE were previously reported in dogs. 4 No cerebellar or other abnormalities were present grossly and there was no histological evidence of neuronal degeneration or inflammation. The most common reported malformation in CH is a stenotic mesencephalic aqueduct,4  which was the presumed cause in the current case, since no other lesions were present. In the current case, the formation of CSF must have equilibrated with absorption, resulting in a compensated hydrocephalic state, until an acute blockage of the ventricular system occurred, resulting in rapid decompensation.

Keywords: Canine, cranial deformity, dog, fetus, occipital dysplasia

References

1. Harrington MK, Bagley RS, Moore MP: Hydrocephalus. Vet Clin North Am Small Anim Pract 1996;26:843-856.
2. Nobre Pacifico Pereira KH, Cruz Dos Santos Correia LE, Ritir Oliveira EL, et al: Incidence of congenital malformations and impact on the mortality of neonatal canines. Theriogenology 2019;140:52-57.
3. Kobatake Y, Miyabayashi T, Yada N, et al: Magnetic resonance imaging diagnosis of Dandy-Walker-like syndrome in a wire-haired miniature dachshund. J Vet Med Sci 2013;75:1379-81.
4. Estey CM: Congenital hydrocephalus. Vet Clin Small Anim 2016;46:217-229.

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.