Neurology Flashcards
What are the two main neurotransmitter in autonomic nerve system and what are the fibers they are secreted from?
Acetylcholine - cholinergic nerve fiber
Norepinephrine - adrenergic nerve fiber
Component of complete neurological exam
- mentation
- gait
- cranial nerve
- segmental reflexes
- proprioception
- palpation
- nociception
Paresis vs plegia
Paresis = weakness
Plegia = paralysis
True or False:
In the autonomic nerve system, all the pre-ganglionic neurons are cholinergic, no matter they belong to sympathetic or parasympathetic.
True
What are the differences between muscarinic and nicotinic receptors?
Muscarinic:
- G protein receptors
- Locates at all the effector cells at the end of all the parasympathetic nerve ending and some sympathetic nerve ending (e.g. sweat gland)
Nicotinic:
- Ligand-gated ion channels
- Locates at the autonomic nerve system synapses between preganglion and postganglion, somatic nerve ending (skeletal muscles)
Is SNS or PNS also called craniosacral division of ANS?
PNS
- SNS is also called thoracolumbar division of the autonomic nerve system
Parasympathetic nerve fibers leave the CNS through which cranial nerves and which nerve in the sacral region?
3, 7, 9, 10 (75%)
Pelvic nerves
What is the resting membrane potential for neuron?
-70 mV
Which part of the brain do thalamus and hypothalamus belong to?
Forebrain
Where is medulla oblongata?
Brainstem (connecting the brainstem to the spinal cord)
Where are the grey matter and white matter in the brain and spinal cord?
Brain: grey matter outside, white matter inside
Spinal cord: grey matter inside, white matter outside
Which spinal nerve root carries afferent neurons and which one carries efferent neurons?
Dorsal: afferent neurons
Ventral: efferent neurons
On MRI T1-weighing, what tissue is hyperintense and what tissue is hypointense? What about T2-weighing and fluid attenuated inversion recovery (FLAIR)?
T1:
- Fat hyperintense
- Fluid (e.g. CSF) hypointense
T2:
- Fluid and tissue with high fluid content hyperintense
- Fat variable
* also called “pathology scan” → inflammation, bleeding, edema will be whither
FLAIR
- Pure fluid (e.g. CSF, cystic fluid) become hypointense → facilitate differentiating
What is the difference between acute brain hemorrhage and chronic brain hemorrhage on the MRI T1 and T2 window?
T1
- Acute (< 24 hours): isointense or hypointense
- Chronic: hypointense
T2
- Acute: hyperintense
- Chronic: hypointense
Describe decerebrate rigidity and the lesion localization.
Stupuros/comatosen + opisthotonus and extension of all limbs
Lesion: rostral pons and midbrain
Describe decerebellate rigidity and the lesion localization.
Normal mentation + opisthotonus with extensor rigidity of the thoracic limbs and either extension or flexion of the pelvic limbs is present
Lesion: cerebellum
Describe Cheyne-Stokes breathing.
Periods of hyperpnea alternating with periods of apnea; can be seen with diffuse cerebral or thalamic disease and metabolic encephalopathies
Describe central neurogenic hyperventilation and the lesion.
Persistent hyperventilation that may result in respiratory alkalosis
Midbrain lesions
When a patient has decrease or absent PLR, where is the lesions?
Midbrain, CN II & III (PNS)
When a patient loses its oculocephalic reflex, where is the lesion?
CN 3, 6, 8
How will the left eye CN II injury affect the PLR?
When light shines to the left eye, there will be no PLR in both eye; when the light shines to the right eye, there will be direct and consensual PLR in both eyes
How will the left eye CN III injury affect the PLR?
When the light shines to the left eye, there will be consensual PLR to the right eye but no PLR in the left; when the light shines to the right eye, there will be direct PLR at the right eye but no consensual PLR to the left eye.
When the patient is miotic and there is no ocular injury, where is the lesion?
diencephalon (e.g. thalamus, hypothalamus)
- Hypothalamus is the origin of SNS pathway
What are the three categories of seizures?
1) Reactive
2) Structural
3) Idiopathic
What is MOA for phenobarbital?
Bind to GABAa receptor and enhance its activity (between beta and gamma subunits)
AMPA antagonist
Ca++ channel inhibitor
How do you load phenobarbital?
4 mg/kg IV q6h for 4 doses, and then switch to 2.5 mg/kg PO q12h
What are the 4 nerves that come from the S1-S3?
Sciatic, pelvic, pudendal, perineal nerves
What are the 5 nerves that come from the L4-S1?
Femoral, pelvic, sciatic, pudendal, obturator nerves
Describe Schiff-Sherrington phenomenon and the pathophysiology.
- Thoracic limb extension and inability to move the pelvic limbs normally. Normal CP at thoracic limbs. Normal spinal reflex at pelvic limbs.
- Indicates T-L spinal cord injury
- Pathophysiology: a lack of ascending inhibitory input to the thoracic limbs originating from the border cells located in the lower thoracic and lumbar spinal cord
- Border cells are responsible for tonic inhibition of extensor muscle α-motor neurons in the cervical intumescence.
When you see two-engine gaits, it most likely indicates which part of the spinal cord injury?
C6 - T2
Thoracic limb: short-stride gait
Pelvic limb: spinal ataxia
Define spinal shock.
Profound depression of segmental reflexes caudal to a lesion, despite reflex arcs remaining physically intact
- It can be up to 12-24 hours after injury
True or False: The spinal cord extends more caudally in cats compared to dogs.
True
When a patient has ventrolateral strabismus, it indicates which CN dysfunction?
CN III
True or False: Trigeminal nerve has both sensory and motor function.
True
What are the three branches of trigeminal nerve and which one has both sensory and motor function?
Ophthalmic (sensory only)
Maxillary (sensory only)
Mandibular (both motor and sensory)
What does the palpebral reflex test for?
Sensory - trigeminal nerve (CN 5)
Medial canthus (ophthalmic branch)
Lateral canthus (maxillary branch)
Motor - facial nerve (CN 7)
What does menace response test for?
CN 2, 7
Which CN is responsible for tear production?
CN 7
What does the pelvic limb withdrawal reflex test for?
L6-S1 and sciatic nerve
What does the patellar reflex test for?
L4-L6 and femoral nerve
What does the gastrocnemius reflex test for?
L7-S1 and tibial nerve
Why KBr is not recommended in cats?
Can cause pneumonitis
What is the recommended serum phenobarbital level in dogs? When should you pull the blood after drug administration?
15-35 mcg/dL (higher than 35 mcg/dL is usually associated with liver injury)
6-8 hours after drug administration
What is normal serum KBr level in dogs?
When KBr is used alone: 0.8 - 3 mg/ml
When combined with phenobarbital: 0.8 - 2.4 mg/ml
True or False: For vestibular ataxia, the side of the head tilt usually indicates the side of the lesion.
True
What is the normal range of intracranial pressure?
5-12 mmHg
What is the formula for cerebral perfusion pressure?
CPP = MAP - ICP
What are the three mechanisms to maintain ICP?
1) Cushing reflex
2) Autoregulation
3) Volume buffering
Explain Monro-Kellie doctrine.
The sum of volumes of brain, CSF, and intracranial blood is constant. An increase in one should cause a decrease in one or both of the remaining two
Explain how the brain autoregulates the cerebral blood flow.
1) Pressure autoregulation
- When the CPP is within the range of 50-150 mmHg, the brain is able to maintain the stable cerebral blood flow via vascular myogenic reflex
2) Chemical autoregulation
- High PaCO2, low PaO2, high H+ → vasodilation
Explain the pathophysiology of Cushing reflex.
Decompensated intracranial hypertension → decreased cerebral blood flow and increased CO2 → catecholamine release → systemic vasoconstriction → activates baroreceptors → bradycardia
What is the ideal CPP in dogs and cats?
50 - 90 mmHg
What are the 2 effects of mannitol in treating ICH?
1) Immediate volume expansion effect → improves cerebral blood flow
2) Delayed (15-30 min) osmotic effect → reduce brain water
What is the rate of axon regeneration?
1 mm per day
What are the muscles that are affected in masticatory myositis?
Temporalis
Masseter
Pterygoid
Describe the pathophysiology of acquired myasthenia gravis
The body starts to produce autoantibodies against the nicotinic acetylcholine receptors (AChR) at the neuromuscular junction of the skeletal muscles. These autoantibodies lead to compliment-mediated destruction of AChR, reduction of functional receptors, and decreased muscular responses to the acetylcholine release, which at the end impair the transmission of action potential from nerve to muscles and results in muscle weakness.
- This is a type II hypersensitivity
** There are 3 main mechanisms for loss of functional AChRs at the neuromuscular junction. The first involves complement-dependent lysis of the postsynaptic membrane caused by antibodies bound to AChRs and simplification of the postsynaptic membrane. Secondly, antibodies can cross-link AChRs on the surface of the membrane leading to increased internalization of AChRs, a decrease in the receptor half-life and decline of the total number of AChRs. In people, the half-life is reduced to 3 days from a normal of 10 days.9 Lastly, antibodies may directly inhibit AChR function.
Reference:
Textbook of Veterinary Internal Medicine,
Khorzad, R., Whelan, M., Sisson, A. and Shelton, G.D. (2011), Myasthenia gravis in dogs with an emphasis on treatment and critical care management. Journal of Veterinary Emergency and Critical Care, 21: 193-208. https://doi.org/10.1111/j.1476-4431.2011.00636.x
List 5 differentials for lower motor neuron diseases.
1) Acquired MG
2) Acute idiopathic polyradiculoneuritis
3) Tick paralysis
4) Elapid snake envenomination
5) Hypothyroidism
6) Paraneoplastic syndrome
What is the dose for Tensilon test?
Edrophonium is a short-acting anticholinesterase (last 10 minutes)
0.1-0.2 mg/kg IV
- Alternative: neostigmine 20 mcg/kg IV
Cholinergic crisis is a dangerous adverse effect from Tensilon test. Name 5 clinical signs and what is the recommended treatment?
Cholinergic crisis is acetylcholine overload at neuromuscular junctions secondary to inhibition of acetylcholinesterase
Clinical signs: hypersalivation, diarrhea, urination, increase bronchial secretion, bronchoconstriction, bradycardia, AV block, muscle twitching
* Patient can be in respiratory distress if the nAhR is overstimulated
Treatment: atropine 0.025 mg/kg IV
True or False: In dogs with acute idiopathic polyradiculoneuritis, cranial nerve usually is not affected; while in dogs with botulism, cranial nerve is often affected.
True
What type of bacteria cause tetanus?
Clostridium tetani
Gram (+), motile, noncapsulated, anaerobic, spore-forming bacteria