37.congenital brain dz

Question 1

two major processes of CSF production

Answer 1

1. choroid plexuses in ventricles via carbonic anhydrase (energy dependent)2. cellular elements

Question 2

congenital hydrocephalus damage caused

Answer 2

–destruction of ependymal lining of ventricles–white matter damage from interstitial fluid accumulation–eventually neuronal injury of cerebral cortexyoung, toy breeds, brachycephalic

Question 3

what causes hydrocephalus

Answer 3

1. obstruction of CSF flow (mesncephalic aqueduct stenosis)2. insufficient absorption of CSF into venous system via arachnoid vili3. hydrodynamic theory of decreased intracranial compliance from defect in brain capillaries (decreases absorption of CSF)

Question 4

PE findings in dogs with congenital hydrocephalus

Answer 4

–fontanelles–large dome shape head–VENTROLATERAL strabismus (setting sun eye)–signs of forebrain disorder (seizure, circle, behavior change, mentation change)

Question 5

internal vs external hydrocephalus

Answer 5

internal–vast majority; dilation of the lateral ventriclesexternal–bulk of CSF accumulation is within subarachnoid space overlying brain and causing the brain to be displaced axially

Question 6

medical tx hydrocephalus

Answer 6

–prednisone (may decr CSF production)–furosemide (inhibits Na/K/Cl co transport decreases CSF production)–acetazolamide (carbonic anhydrase inhibitor–inhibits enzyme responsible for CSF production)–omeprazole (H pump inhibitor–decreases CSF production in dogs by 26%)guarded prognosis

Question 7

sx tx hydrocephalus

Answer 7

surgical shunting procedures–px varies 50-90%shunt in vet med are PASSIVE–ventricular catheter into lat ventricle–one way valve–peritoneal catheter

Question 8

surgical shunting procedure complications for tx hydrocephalus

Answer 8

shunt obstructionshunt dislodgmentmechanical damage to shuntshunt infection

Question 9

define intracranial arachnoid cyst

Answer 9

CSF accumulation within a split of the arachnoid membrane during embryogenesisfluid may be secreted by the arachnoid cells lining the cyst cavityfluid moving INTO the cyst may occur via an osmotic gradient

Question 10

location of canine intracranial arachnoid cysts

Answer 10

caudal fossa (cerebellum and brainstem)can be an incidental findings in 1/3 to 1/2 of reported cases

Question 11

sx treatment of intracranial arachnoid cysts

Answer 11

–cyst fenestration (cyst can still persist)–cystoperitoneal shunt placement

Question 12

chiari like malformation

Answer 12

aka: caudal occipital malformation syndrom, occipital hypoplasiacranial cavity is too small (skull is malformed) to hold caudal fossa contents (cerebellum/brainstem)more specifically, caudal malformation seen is of the supraoccipital bone causing an indentation on caudal cerebellum +/- cerebellar herniation (40%) through foramen magnum+/- cervical syringomyelia/syrinx formation/hydromyelia

Question 13

3 theories of fluid in syrinx being CSF

Answer 13

1. water hammer: systolic P wave forces CSF into fluid filled syrinx cavity2. piston: systole cerebellum moves caudally, diastole cerebellum moves cranially–changes in fluid movement3. suck: CSF is sucked into the syrinx

Question 14

breed predisposed to chiari like malformation and clinical signs associated

Answer 14

Cavalier King Charles Spaniel (40% asymptomatic)clinical signs: PAIN (neck, back), vestibular dysfunction, incessant scratching activity, scoliosis, cervical myelopathy

Question 15

an enigmatic ear problem of CKCS

Answer 15

primary secretory otitis mediaclinical signs may be similar and include pain, scratching, head tilt etc.breed also has congenital deafness and idiopathic epilepsy (unknown if all of this is related or not)

Question 16

tx for chiari like malformation

Answer 16

symptomatic–analgesics, decr CSF production, GCC, gabapentinsurgical decompression (sub occipital craniotomy) of foramen magnum: titanium mesh with PMMA cranioplasty

Question 17

MOA of gabapentin

Answer 17

can be used to treat neuropathic pain associated with syringomyeliaselectively binds alpha-2-delta 1 subunit and inhibits calcium influx into nociceptive neurons pregabalin has longer half life and can be used at BID dosing

Question 18

prognosis and relapse rate following decompression for chiari like malformation

Answer 18

short term success–80%relapse 25-47% likely from excessive scar formation

Question 19

atlanto occipital overlap

Answer 19

C1 is overlapping the foramen magnumtoy breed dogscan compress cerebellum and cause medullary kinkingcan be seen alone or in combo with chiari like malformation

Question 20

dorsal constriction C1-C2

Answer 20

malformation of dorsal C1-C2 leading to dorsal compression in small and toy breed dogsinstability likely present