Cerebellar hypoplasia (non-human)
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This article has some general information, but focuses primarily on CH in the domestic cat.
In cats, this condition is also called "Wobbly Cat Syndrome." An animal with CH may be called ataxic or be described as a "bobble-head."
Function and development of the cerebellumEdit
The cerebellum is the brain's main control center for planning, adjusting, and executing movements of the body, the limbs and the eyes. It plays a major role in several forms of motor learning, including balance and posture.
In the past, the evidence for a role for the cerebellum in cognitive functions was rather weak. However, investigations into the cognitive neuroscience of the cerebellum are rapidly advancing, extending far beyond the traditional view. For humans, current theories support that what the cerebellum does to sensorimotor and vestibular control, it also does to cognition, emotion, and autonomic function. How it functions in cognition, emotion, or autonomic function in animals is still largely unknown. In 2012, a study in mice provided direct evidence that subtle disruptions in cerebellar architecture can have pronounced effects on behaviors typically associated with autistic-like behavior.
Development of the cerebellum starts in a fetus in utero and, depending on the species, may continue for some period after birth. Postnatal development periods vary by species including: dogs up to 75 days, cats to 84 days, calves up to 6 months.
Feline panleukopenia ("FPLV" a.k.a.: Feline Distemper or Feline Parvo) virus has long been known to cause cerebellar hypoplasia in neonatal kittens through in utero or perinatal infection. In utero, the virus can pass from the dam to the developing fetus and may then disrupt the development of its cerebellum by hindering cell division. This can happen when the dam is actively infected with the virus or given a modified-live FPV vaccine when pregnant. If young kittens are infected by this virus during or after birth, and survive, the active virus can disrupt the postnatal cerebellum development. If kittens are given a modified-live FPV vaccine too early, while their cerebellum is still developing, it may cause CH.
In most cases the cause is unknown. However, in dogs and cats it is thought to be most likely related to in utero viral infections, toxins or genetic disorders.
Other possible causes, if they occurred during the development period of the cerebellum and inhibit its growth, include:
- Malnutrition, either from a lack of adequate critical nutrients or an inability to absorb them
- mycotic infection
- Protozoal infection (e.g.: toxoplasmosis)
- rickettsial infection (most are spread through ticks, mites, fleas, or lice)
- Traumatic brain injury
- Viral infection (e.g.: feline infectious peritonitis)
Depending on the specific area(s) and amount of cerebellum affected, the severity at which the animal displays problems varies. Some signs may be seen immediately after birth. Perinatal kittens with CH may have difficulty getting to the mom's nipples, competing with siblings, and problems suckling and/or swallowing.
As a kitten ages, signs may become apparent when it starts to become mobile and attempts to stand/and or walk. It may display jerky movements, tremors, rolling around instead of starting to stand and walk, swerving, head bobbing, falling, and generally uncoordinated motion. Some animals may never be able to walk. Sometimes signs are so subtle they are not noticed except under careful observation and as the animal becomes more mature.
Cerebellar hypoplasia may be exhibited by some or all of these, at various levels of severity:
- Decreased muscle tone (muscle hypotonia)
- Inability to control range of movement
- Inability to correctly sequence fine, coordinated acts
- Inability to perform rapid alternating movements
- Inability to vocalize correctly
- Involuntary, rapid oscillation of the eyeballs in a horizontal, vertical, or rotary direction (nystagmus)
- Reeling, wide-based gait (ataxia)
- Tremors (Intention tremors are alternating, oscillatory movement of a limb or the head as it approaches a target. Postural tremors are tremors in the body or extremities when a fixed posture or weight bearing is attempted.)
Levels of severityEdit
There is a very active U.S.A-based Facebook page for Cerebellar Hypoplasia Cats and Kittens ("Dogs and Puppies, too"). It has well over 10,000 members from locations all around the globe. The originating organization, chcat.org has been instrumental in introducing a rating scheme for CH cats that is widely accepted and used among its members.
What follows is based primarily on their rating scheme and on an adult cat's ability in its living environment. It does not reflect a neurological assessment of the actual damage to the cerebellum. Temporarily, during growth periods or when ill, stressed, or tired, a cat may seem slightly "worse" than usual.
This mild-to-severe rating should be viewed as a general guide and a scale. Cats may be described as very mild, mild, mild-moderate, moderate, moderate-severe, severe, extremely severe, and may, or may not, exhibit some or all of the following.
Very capable. Requires little to no extra care. Some home accommodations may be helpful.
- Unusual gait. A high step or waddle.
- Occasional balance loss.
- May have subtle head tremors when focused, excited or stressed.
- Can walk, run, jump, and climb.
Can get around on their own. One end of their body may appear to be doing something else than the other end. A modified living area to prevent injuries from stumbles and falls may be necessary. Some aids to assist in accomplishing essential daily tasks (eating, drinking, voiding, staying clean) may be helpful or necessary.
- Walk with legs splayed in a wide stance.
- May have a notable "bunny hop" with the back legs when running.
- Frequent balance loss and falls.
- Noticeable head tremors, especially when focused, excited or stressed.
- Can usually climb, but uses claws to latch on and pull up.
Cannot stay standing or walk on its own, except for maybe a few steps. Requires significant adjustments in their living area(s) to protect them from getting hurt when they move around and to accomplish essential daily tasks (eating, drinking, voiding, staying clean).
- May flip and flop to get around.
- May not be able to get to, or use, a litter box. Some may need bladder manually expressed.
- May be able to use claws, by latching onto fabric/carpet, to move around or up.
- Constant head tremors.
A definitive diagnosis of CH can only be made with brain imaging (MRI). A clinical evaluation is necessary to rule out other, contributing, or confounding factors and to establish that the presenting signs are stable. CH is not a progressive disease, so the presenting clinical signs and history should not indicate an overall worsening of the animal's abilities.
Due to the cost and risks factors of having an MRI done, or a lack of access to adequate veterinary services, many owners opt for a probable diagnosis based on observation and/or clinical evaluations.
General practice Veterinarians may or may not be familiar with CH. It is not uncommon for it to be misdiagnosed, with numerous unrelated ailments being attributed to it or when the neurological problem is clearly progressive. Consultation with a Vet Neurologist is advisable; they specialize in disorders of the nervous system: diagnosing and treating diseases of the brain, spinal cord, peripheral nerves, and muscles.
Numerous problems can be mistaken for CH. These include (but are not limited to):
- Ataxia: vestibular or sensory
- Brain or spinal tumors or lesions
- Cerebellar abiotrophy (a.k.a.: cerebellar degeneration). This can easily be mistaken for CH if it manifests early in the life of an animal. It has been identified in numerous animals, including: cats, dogs, horses, cattle, and sheep. Cerebellar abiotrophy occurs when Purkinje cells in the cerebellum start to die. Unlike CH, however, this occurs after the animal is born, causing normally developed cells to die. It is a genetic disease and may be hereditary in some species.
- Ear polyps
- Exposure to toxins
- feline infectious peritonitis (FIP)
- Inner ear infection
- lysosomal storage diseases
- Nutritional deficiency
- Physical trauma, traumatic brain injury
- Toxoplasmosis
There is no standard course of medical treatment for cerebellar hypoplasia; it cannot be cured. Generally, treatment is symptomatic and supportive. When the CH is severe and supportive home care is not available, or is not sufficient, or the quality of life would be poor, affected animals are euthanized.
General medical care and treatment of the CH catEdit
Except as noted below, if otherwise healthy, general medical care for a CH cat is no different from that for a non-CH cat. They can breed and are susceptible to the same diseases, infections and parasites. Normal preventive care applies for:
- Spay or neuter
- Dental care
- Parasite prevention (with the exception of some flea/tick agents that are contraindicated for cats with neurologic abnormalities)
Cats, especially CH cats should never be declawed. Their claws are essential aids for mobility and stability. It is usually OK to trim the tips of their claws, although some members of the CH Cat Facebook group have reported that even this causes a notable decrease in ability.
- Anesthesia: In 2004, a study was published that linked ketamine to post-anesthetic cerebellar dysfunction in cats. 11 cats that did not have any indication of cerebellar deficits before surgery, did after. All of these cats were Persian crossbreeds. Ketamine can cause erratic and spastic, jerky movements and muscle tremors and is slow to be metabolized out of the system. Members of the CH Cat Facebook group routinely advise against its use. The 2018 American Association of Feline Practitioner's Feline Anesthesia Guidelines lists numerous alternatives. Gas anesthesia offers a number of advantages in many circumstances. In CH cats the rapid recovery is its primary advantage.
- Medications: Medications that may cause ataxia or have other possible neurological side-effects should be carefully considered before being used. Those side-effects may be extra difficult for a cat that is already wobbly. Some medications are specifically contra-indicated in cats with neurologic deficits/disease.
Complementary and alternative veterinary medicine (CAVM)Edit
The physical deficit of the cerebellum does not get better or worse with age. Mild-to-moderate CH cats can usually learn to compensate for some or all of the associated mobility issues. Very young cats can appear to make dramatic improvements as they mature, but this is primarily due to them developing their muscles and stamina, and from learning and adjusting.
Physical therapy may help a cat develop and maintain muscle tone and stamina, in turn enabling it to achieve and maintain more mobility and flexibility than it might have been able to achieve if left to develop on its own. In addition to the CAVM treatments listed above, support harnesses or slings and mobility carts (a.k.a.: quad wheelchairs) may be helpful. There are numerous types and styles available commercially. There are also good do-it-yourself tutorials and pictures on-line.
Providing that the root cause of the CH did not affect other parts of the developing animal, it can, in theory, lead a fairly normal life and have a normal life-span if special considerations for its disability are taken by the owner. However, secondary complications, such as accidental injuries that occur as a result of the condition, or complications from a sedentary lifestyle for mobility-limited cats, may affect their overall health and lifespan. CH cat owners can be proactive to help prevent these secondary complications and to integrate exercise into the daily routines.
If the root cause of the CH impacted other parts of the developing brain and/or body, the overall health and life-span may or may not be impacted. For instance, fetuses infected in utero by FPLV that survive, and kittens less than a few weeks of age that become infected with it, can also have retinal dysplasia, and optic neuropathy.
Home care considerations and accommodationsEdit
Some CH cats do just fine without any extra care or special home accommodations. Others need a little help to navigate the home without getting injured or to accomplish their daily living tasks. As the level of severity increases, so does the intensity of care that may be required. This includes not only help with getting around, or getting around safely, but also cleaning up their messes and their body.
For mild-to-moderate CH cats, it is important to know that their ability to respond "instinctively" to a threat (scare/startle) may not be inhibited. Bolting, biting, scratching and clawing when scared or startled are instincts, and are controlled by a different portion of the brain. A mild-to-moderate cat that can't walk a straight line, could dart straight away in a flash.
CH cats don't understand that they are disabled, so they will not be self-inhibited from trying to climb or descend. Prevention of injuries requires careful consideration of the specific hazards posed by where they live and their potential abilities. Some cats that cannot walk well or jump, can still climb extremely well. Don't assume a CH cat can't or won't try to get up on something; it is in their nature to explore, jump, and climb. A cat can grip with its claws to get where it wants to go.
There is no "one size fits all" answer for how to address and help the unique needs of a specific level of CH cat.
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