CANINE HYDROCEPHALUS
- kradiganscience24
- Oct 30
- 4 min read
Tavishi
I am now in my third week of college (second week of actual classes) and am in the process of trying every single club possible. I am so desperately lost and so excited about everything.
So far, I've joined Anatomy (but not getting their emails?), Pathology, Parasitology (or, well, trying to join? I don't know how to contact their administration.), Nerd (I'M NOT ON THEIR EMAIL LIST BUT I FILLED OUT THEIR FORM LIKE 5 TIMES?), Zoology (I don't know whether or not I am a member officially?), Sub Aqua (I have no goddamn idea how to officially join this?), and Neurology Society. I am lost in the hell that is email lists, QR codes, whatsapp groups, and Instagram accounts. This is so confusing but I'm just trying to go to whatever I can! I've attended a lot of events, but I think I've gone to two really fun ones so far: ZooSoc's invertebrate handling practical and the first meeting of the year for Neurology Society.
Another really interesting event I've gone to that didn't involve fluffy little creatures was the first neurology society meeting of the year. It was just a bunch of dudes on Zoom at the other campus yappin about the research they've done on neurology, but it was so interesting. My biggest takeaway was "oh my god I forgot how cool the nervous system was", then went home and got to reading Miller's neurology chapters.
Hydrocephalus is a condition where there is excess cerebrospinal fluid in the brain, causing increased intracranial pressure. This can be caused either by overproduction of fluid or issues with drainage. Cerebrospinal fluid is the soup of the central nervous system surrounding the brain and spinal cords, and also flowing through the ventricles of the brain. It is produced by ependymal cells, of which the internal lining of ventricles consists.
Within the dog, there are two lateral ventricles, one on each side of the cerebrum. These are the largest cavities carrying CSF. Then, there's the third ventricle, which can be found in the diencephalon (region of the brain where the thalamus, hypothalamus, and epithalamus is). There is also one fourth ventricle, located near the brainstem.
These ventricles are connected by four foramina. First, the foramen of Monro, connecting the lateral ventricles to the third ventricle. These are also called the interventricular foramina.
The foramen of Sylvius, or the cerebral aqueduct, connects the third and fourth ventricles. The foramen of Magendie is a hole in the fourth ventricle that takes cerebrospinal fluid to the cisterna magna, or the weird external region between the meninges around the cerebellum and medulla oblongata. Finally, the foramen of Luschka carries CSF from the fourth ventricle to the subarachnoid (in between the meninges) cistern between the cerebellum and the corpus callosum.
Hydrocephalus in dogs takes many different forms, based off the different causes and issues. Hydrocephalus is very commonly a complication of other pathologies, like traumatic brain injury, bacterial meningitis, etc. Congenital hydrocephalus (condition present from birth, rather than as a complication later on in life) can taken many forms, including internal, external, etc.
Two common forms of hydrocephalus present in congenital patients are internal and external hydrocephalus. Internal hydrocephalus is the build up of CSF within the ventricular system, whereas external hydrocephalus is the buildup of CSF within the subarachnoid space (as mentioned earlier, the little gap between the meninges where CSF is oft deposited). Internal hydrocephalus can also be a complication of meningitis, tumors, and other similar issues. External hydrocephalus is especially known to be caused by bacterial meningitis, in addition to a congenital birth defect. A more proximal cause of external hydrocephalus is a blockage of the fourth ventricle.
To put all of this in simpler terms: in internal hydrocephalus, fluid isn't being deposited into the cells it needs to go. In external hydrocephalus, it's being put where it's supposed to by the ventricles, but there's just way too much CSF stuck in the subarachnoid space.
Communicating hydrocephalus is similar to external hydrocephalus in that it involves fluid build up in the subarachnoid space. Conversely, whereas external hydrocephalus does not generally involve ventricular dilation, communicating hydrocephalus does. The issue with communicating hydrocephalus is a blockage with the absorption of CSF from the subarachnoid space.
Non-communicating hydrocephalus, on the other hand, is a blockage preventing flow of CSF between the different ventricles, usually caused by stenosis of the foramina. Foramina typically blocked are Monro (lateral ventricles to third ventricle) and Sylvius (third to fourth ventricle). Stenosis of the foramen of Sylvius (also known as ventricular aqueduct) is a common congenital cause of hydrocephalus, often caused by issues in neural tube folding. Another cause of aqueductal stenosis is growth of a tumor.
Note: at this point in writing my post, two clowns appeared:
Congenital canine hydrocephalus is found predominantly in two groups of dog breeds: the brachycephalic and toy breeds. These include chihuahuas, Boston terriers, pugs, cavalier king charles spaniels, etc.
Moral of the story: excessive breeding and artificial selection has a myriad of consequences echoing into the life of animals. Just because it makes an animal "cuter", doesn't mean your artificial selection and irresponsible breeding is harmless. I have literally never met a brachycephalic dog with good quality of life. Almost every single brachycephalic dog I've met in the shelter either has hydrocephalus or cherry eye, and is almost certainly wracked with a dozen other comorbid conditions, and on top of all of this can't freaking breathe.
I could go on for ages about canine hydrocephalus, because it is such a wide-spanning topic. There are so many different intricacies involved with its congenital defects, as well as with more traumatic causes of injury.
But for the sake of my readers' attention spans (why do y'all stop reading after like 30 seconds unless I add an absurd amount of images?!!), I'll cut myself off here, though.