---start---- Dr Washabau is back. Exam results are back. He needs 24 hrs to do exam analysis. We should get them back tomorrow. Dr Sweeney (him) slide room is locked so we have no slides right now. Bovine neurology: brain and brainstem: [did you hear about the circus fire? the heat was intense...][ha ha] How to do a neurological exam - the neuro exam has an aura of mystery about it that maybe it shouldn't....he's not a neurologist so is going to give us the large animal slow and dumb approach to doing a neurological exam (joke). this should simplify things for you. Start at the front, and work back. compartmentalize things - lesions of different parts of CNS cause different signs. First part of neuro exam - make an anatomical diagnosis, localize the lesion. then make a list of differentials. if you make a diagram of the CNS - cerebrum cerebellum brainstem cervical cord TL cord CS cord intumescences at C6-T2 and L4-S2 Hallmarks of cerebral disease: seizures, blindness (with intact PLR but no menace, can't navigate obstacle course), depression, changes in mentation, abnormal behavior with aggression or compulsive behavior or self-mutilation, head pressing, etc. may see altered gait but really large animals don't show much of a change in gait even with major cerebral lesions. Hallmarks of Cerebellar Disease: ataxia, intention tremor (the key clinical sign in large animals - pathognomonic for cerebellar disease), hypermetria, loss of menace response without blindness Hallmarks of Brainstem Disease: cranial nerve deficits. V: trigeminal: motor to mm of mastication, sensory to face including cornea VII: facial: motor to mm of facial expression - in cattle with facial n. paralysis, there is no marked muzzle deviation to opposite side like in horse. loss of menace can be due to facial paralysis or blindness or cerebellar disease. to tell apart - touch eyelid to test palpebral, look to see if it turns head away when you menace it. if it doesn't blink, but moves head, probably facial paralysis. if it can't feel, probably trigeminal. VIII: vestibular: head tilt, nystagmus, loss of balance occur with lesions Cord: evaluate gait, posture, and reflexes. divide into cervical, cervicothoracic intumescence at C6-T2, thoracolumbar cord, lumbosacral intumescence at L4-S2, and caudosacral cord in small animals, you may try to tell apart proprioceptive vs motor deficits, that kind of thing - in large animals, just decide is the animal wobbly or staggering or incoordinated, or is it not? if it is, it has a neuro problem. it is hard to tell apart weakness vs motor deficits vs proprioceptive problems - all manifest as swaying, staggering, stepping on himself, etc. how do we test the reflexes in a standing animal? which are available? panniculus - cutaneous trunci response to pinprick (innervation for that comes off the caudal cervical area, cranial to the intumescence. also the anal reflex - pucker when you touch it - that uses caudosacral segment of cord. in dog you test the patellar tendon reflex - you can't do that in a standing cow but you could in a recumbent cow. same with withdrawal reflex. and you can only do those in the leg that is up. then you'd have to roll the cow over to do the other side. patellar reflex uses the quadriceps which is innervated by the femoral nerve. withdrawal reflex uses the sciatic nerve. remember the femoral nerve comes off more in the cranial aspect of the TL intumescence, and sciatic in the caudal part. but there is a lot of overlap. so lets go through and say we have a lesion - a couple of other important things - motor neurons come off the intumescences. we talk about lower vs upper motor neuron dz, right? if a lesion is not involving the motor neurons, you can affect the limb function but you do not get limb atrophy, and you do not lose reflex function. if you do affect the neurons, you get muscle atrophy and areflexia. when disease affects the intumescences we call it lower motor neuron disease. upper motor neurons are in the brain. LMND causes flaccidity, muscle atrophy, areflexia. so start at back and work forward. you have a lesion of caudosacral segments only. all that is affected is anything caudal to the lesion. gait, posture, reflexes are all normal. the only thing affected are those areas innervated by caudosacral segment, mainly tail and anus. so you may have flaccid anal tone or a tail that does not swish. we don't see this often. sometimes cows with epidurals using alcohol can have this last for a while. lesion at L5, in the middle of the lumbosacral intumescence: anything cranial to that is basically normal. if you wheelbarrow the cow, front legs are fine (ha). hind legs are paretic/paralyzed, flaccid, and hyporeflexic or areflexic. after 7-10 days there is muscle atrophy of hind leg musculature. degree of paralysis is variable - animal may be recumbent, or just wobbly, weak, scuffing, dragging, dog sitting. lesion in thoracolumbar cord - anything cranial to it is ok. front legs are still normal. what about schiff-sherington syndrome? TL lesions in dogs cause forelimb rigidity b/c of loss of ascending inhibition. this is exceedingly rare in large animals. forget it. ok, but what do we see? interruption of motor to hind limb and sensory from hind limb - reflexes of hind limbs are normal, no muscle atrophy occurs, but there is hind limb paralysis/paresis and ataxia. reflexes can be slightly increased due to loss of inhibition. lesion in CT intumescence - hind legs are still abnormal, as with TL cord lesion. HL reflexes intact/hyper, no muscle atrophy, still paralyzed or uncoordinated. front legs have LMND signs - paralysis/paresis, atrophy, areflexia. cervical lesion - all legs show ataxia or paralysis but reflexes and muscle mass are maintained in all four legs. once you make an anatomic diagnosis you make a differential list. no new diseases - you know these all from IMD. cow is blind, seizures, has normal menace, acts aggressively. has a cerebral lesion. what causes those? -trauma -space occupying lesion: abscess (usually younger animal), neoplasia (rare!) -infectious diseases: rabies, pseudorabies ("mad itch"), BSE ("mad cow") -metabolic: ketosis (nervous type = #1 cause of cerebral dz in dairy cattle), thiamine deficiency causing polioencephalomalacia, hypomagnesemia ("grass tetany") -toxic: lead poisoning (r/o for polio), salt toxicity/water deprivation, urea toxicosis, hepatic encephalopathy those are some of the major causes of cerebral disease in cattle. just focus on the fact that you have to localize the lesion based on clinical signs, and know which ddx are appropriate for disease at that site. Cerebellar disease - ataxia, hypermetria, absent menace, INTENTION TREMOR. differential list: not too many things cause cerebellar disease. -in calves - think right away of in-utero BVD infection - BVD crosses placenta and can be teratogenic, can cause cerebellar hypoplasia. if you nurse these calves along they can accomodate, be BAR, eat, be functional cows. -space occupying lesion, abscess that's about that. main thing is in-utero BVD. Brainstem: remember signs associated usually relate to CN deficits; also reticular activating system is here so we see dullness, depression. respiratory centers are here too so could see respiratory arrest but then you wouldn't be doing a neuro exam! ddx list: -listeriosis - most common cause of asymmetric CN signs. usually listeria in silage gets through oral mucosa through abrasion, migrates up trigeminal n. into brainstem, causes microabscesses.signs are variable depending on where these are. usually V, VII, VIII. will be drooling a lot, will get metabolic acidosis from lost bicarbonate from saliva. -other major ddx for facial paralysis and vestibular dz - peripheral damage to VII and VIII occuring at the ear due to otitis media or otitis interna. if there is also trigeminal involvement it's more likely to be listeria. but also with peripheral disease you wouldn't see depression, dullness. you should with listeria. for BAR animal with facial paralysis think peripheral, think ear. -again you could have a mass, abscess. much less common than listeriosis. slides should be set up here. ok. cases: this is a cow with 12 hr history of compulsively pushing into the head gate, driving herself forward, abrasions are appearing on her neck where the bar rubs. she's in peak lactation, 6-7 weeks fresh. what do you want to do? check ketones. yup, nervous ketosis. sometimes these cows also chew front legs, may see hairloss, self mutilation. this is a calf which is unable to stand up well, ataxic, has intention tremor and poor motor control. he has cerebellar hypoplasia due to BVD infection in-utero. this is a cow with who is slobbering, she's normally friendly and docile but now over 2-3 days has developed an aggressive behavior and head-butts everyone who comes in the paddock. ears back. difficulty swallowing. consider rabies. she did in fact have rabies. holstein bull with acute onset right head tilt, right ear droop. circles to right. slightly ataxic, low fever, depressed. brainstem lesion due to asymmetric CN signs - main ddx listeriosis. this was a classic case. he didn't respond to abx so they put him down, and it turned out to be a brain tumor. --break-- one more thing about the cord - telling apart upper motor neuron from lower...the LMN is in the ventral horn of the grey matter and directly innervates the muscle, and is affected by lesions of the spinal cord intumescences, resulting in areflexia and muscle atrophy. the UMN is up in the brain, sends fibers down through long tracts, and synapses on the LMN, giving instructions. lesions above the intumescence will affect the axons of the UMN causing signs of UMN disease - paralysis, paresis, ataxia, proprioceptive deficits. no atrophy, no areflexia. ok. so we talked about localizing lesions and making ddx lists. now, if your neuro exam suggests a problem in the spinal cord, what kind of differentials do you suspect? most of the diseases can affect any cord segment - signs relate more to location than to etiology. we'll go through one at a time. Trauma: always consider trauma first - fractured vertebra. a couple of characteristics of trauma - the progression is such that signs are the worst during the first 24 hrs, then they do not progress beyond that, usually. also, bovine animals are pretty resilient, so it's fairly unusual for a cow to fracture the spine - they aren't in car accidents, occasionally do get hit by a tractor. if you do dx fractured vertebra, esp in calf b/w 2 mos and 1 yr of age, ALWAYS consider pathologic fracture because this is the one situation where we do see fx vertebrae in cattle more often - due to nutritional osteopenia. we don't see this in calves on milk diets. but sometimes there is a feeding accident - after weaning, calves are put on grain and sometimes poor quality hay and sometimes the diet is inadequate in calcium, and bone doesn't mineralize well, and they get pathologic fx of any bone - long bone, rib, vertebrae, whatever. can present as herd outbreak of recumbent calves. you think there's been a toxin and you start doing PEs and find broken bones. treatment: you know that Far Side cartoon? broken leg: shoot. sadly, regardless of the cause of some of these conditions, treatment is generally to euthanize. if the animal has fractured vertebra and cord compression, it's usually not economically feasible to treat. so generally we euthanize these animals. the next thing to consider: Abscess: can be located in the spinal cord itself, which is fairly rare, or more often in the vertebral body. think about the anatomy - if you have an abscess in the bone and the cortex of vertebral body is intact, fine. but eventually the cortex will erode and bone may fracture, or infection will ooze out and cause myelitis, or whatever. usually osteomyelitis is more in young animals. a 5 yr old cow with cord disease isn't a prime suspect, but if cow is under a year, abscess is more likely. the most common organism involved is actinomyces pyogenes. how do we make the diagnosis? can attempt radiographs but if cow is big you may not pick up a lesion. if there is a meningitis, a CSF analysis should show increased cell count, neutrophils, increased protein. bottom line, though, treatment after the onset of signs of cord disease is generally ineffective and we end up euthanizing them. antibiotics don't usually work. the third disease - that can cause spinal cord compression or disease in cattle is something we see in older cattle: lymphosarcoma. LSA you recall is about the most common internal neoplasia of cattle, seen in BLV+ cattle. the things to remember are that first of all, 20-50% of cows in the US have this virus but only a few ever get cancer. the predilection sites for the tumors are heart, abomasum, LNs, then spinal cord is fourth or fifth on the list. clinical signs appear in older cows, >3 yrs. usually involves the lumbar or lumbosacral cord. rarely involves the front legs. also, the tumor masses are extradural, so pia mater is on cord, then arachnoid, and on top of that is the dura, right? and the fluid is in the subarachnoid space b/w pia and arachnoid - so a CSF analysis on cow with LSA should not be expected to contain neoplastic cells. these masses are outside the dura. so to dx this, uusally these cows have some big LNs somewhere - you could biopsy those. they might have other tumors too, although often they don't, so it can be hard to confirm the diagnosis, but - if it's positive for BLV, that is supportive but many normal cows are positive. a negative BLV test rules out LSA pretty much. but if you have aged cow with hind end paralysis, +/- reflexes present, no history of trauma, BLV+, lymphosarcoma is high on your diff list. another condition, we don't see this often but sometimesin aged bulls - bridging spondylitis - old age arthritic change, especially in bulls on farms that have been fed high calcium rations. they get proliferative bony lesions causing sore back and eventually can cause cord compression. more in bulls than cows. so cord disease in cattle is easy. think of trauma. then if young, think osteomyelitis, if old think of LSA. that's really the basics. slides: this cow is dog-sitting (no, she's not watching your dog while you are out of town, she is sitting like a dog). hind end paralysis is present. another clue to a neuro problem is she's been clipped for a spinal tap. we don't know what she had but her hind legs were paralyzed. assume 4 yr old cow, midlactation, walking funny then 2-3 days later down and can't get up. owners asked about milk fever. but she's in midlactation. she's BAR and front legs are normal. intact reflexes but can't get up in hind end. no history of trauma. gradually progressive signs anyway so not like trauma. hind legs paretic, no muscle atrophy, normal reflexes, front end normal. lesion must be in thoracolumbar cord. etiology? most likely to be LSA - she's >3. four month old calf, progressive difficulty moving, can't get up without assistance but can stand if you help it up. forelimbs normal. hind limbs ataxic, paretic, uncoordinated, severe proprioceptive deficits, obviously neurologic in hind legs. front legs ok. reflexes in hind legs are intact. again, TL lesion. ddx: abscess, trauma, nutritional. necropsy: the vertebral body has an abscess in it that has broken out into the canal. this calf did have abnormal CSF. 6 mo old calf in CA - history of going through chute for some reason, and went down in the chute. maybe trauma? didn't see anything in particular. lying in stall with normal front legs but hind leg paralysis. this is a day or two later and the hind limbs are flaccid with no reflexes. so there is a lesion in the LS intumescence L4-S2. ddx for sudden onset paralysis - trauma - this calf had a fractured caudal lumbar vertebra, L5 or L6. it had a compression fracture and this was of nutritional orgin, the bones are osteopenic, you could tell on histology and by flexing the bones. Peripheral nerve lesions of cows: there are a few. what are the characteristics of a peripheral nerve lesion? -usually unilateral (unless animal has two lesions) -usually have muscle atrophy and areflexia in innervated muscle this calf was born 2 days before this picture was taken - dystocic birth. difficulty bearing weight in hind legs since birth. trouble extending the stifle, stands crouched. muscles which extend the stifle are the quadriceps, innervated by the femoral nerve. this calf has bilateral femoral nerve paralysis. we see this following dystocia. everyone always says "oh, must have been posterior presentation" but actually usually anterior presentation during which because of fetopelvic disproportion or malpositioning, the stifle is caught on the brim of the maternal pelvis, and stifles are pushed caudally and femoral nerve is stretched or torn - usually both legs for this. degree of involvement depends on amount of damage. some can't stand at all. some can stand but sort of crouch. prognosis if they can stand and bear a little weight is good - time and antiinflammatories allow recovery over a few weeks, mos. if animal is recumbent and can't bear weight even if you help it, it should be euthanized. slide: bruised, damaged femoral n. this calf is knuckling on left hind, splay legged in front, being treated for diarrhea by owner, 10 days old, head/neck extended. over past 2 days, calf walking with left hind fetlock knuckled under. can't extend fetlock - the sciatic nerve branches innervate those muscles - easily damaged by IM injection of irritating substances esp in calf with minimal muscle mass. prognosis is good, just needs time to recover. you worry about abrasions on the dorsum of the foot - sometimes splinting is required to prevent this. with time it should resolve. so far in hind leg: sciatic (from injection) , femoral (from dystocia) cow knuckling - remember sciatic branches into tibial - which goes superficially over the stifle. this cow was recumbent awhile and when got up was knucking - this is tibial n. paralysis, prognosis good, recovery w/in a few weeks is likely. these cows ambulate pretty well - will even flip the leg to place sole on ground. this cow is 24 hrs fresh, having difficulty getting up since parturition, is splay legged in hind end. this is obturator nerve paralysis, also called maternal obstetrical paralysis. maternal obstetrical paralysis is usually seen in first calf heifers, b/c they are smaller. depending on bull they've been bred to, sometimes they have a calf that is really too big. there are two nerves that can get compressed when calf is born - the obturator and the sciatic. either or both of those may be affected in the cow. the signs depend on which nerve(s) is/are affected. if just sciatic n, you see more knuckling; if just obturator, you see the tendency to abduct the limb/do the splits. if the cow has just obturator nerve affected and is on concrete, she won't be able to get up - will scramble to get up but feet will splay out laterally and she can't get up. but if she is put on good dirt surface she will be able to get up - we put hobbles on to make sure her legs do not splay out too far. if both obturator and sciatic nerves are damaged, then regardless of footing, they won't be able to stand at all. sciatic nerve only - can stand. prognosis good - usually recover within a few weeks. if totally recumbent require nursing care - can use the AquaCow treatment - put in water tank to keep weight off, prevent muscle ischemia. disease of cord that is diffuse - this lamb has tetanus and is in rigid extension. clostridium tetani toxin binds to inhibitory neurons in spinal cord so there is loss of inhibition and rigid extension. cattle are fairly resistant to tetanus and are not routinely vaccinated. what predisposes sheep? tail docking, elastrator band castrating. pigs are probably the most resistant domestic spp we work with and also are not routinely vaccinated, but they too can get tetanus, most often associated with castration. finally - you do not need to know this for exam but there is a congenital disease of cattle which involves dysfunction of the stretch detector mechanism in hind legs, the cow has uncontrolled extension of the hock which is referred to spastic paresis or something heel. it is rare, probably involves abnormality of stretch reflex response. tibial nerves, cord. ----end----