8. Intro and Neurolocalizing in the Brain

1/15/2026; Dr. Sullivan

a neuron completely in the CNS that influences the actions of other neurons

upper motor neuron

a neuron with its NCB in the CNS and axon in the periphery

Lower motor neuron

describe LMN signs

decreased tone, decreased reflexes

describe UMN signs

increased tone, normal to increased reflexes

what are the most reliable spinal reflexes? (4)

-explain what should happen when testing each reflex

• Patellar: tap patellar tendon, look for extension of stifle

• Withdrawal: pinch toe, look for flexion of carpus, elbow, shoulder or hock, stifle

• Perineal: observe anal tone, stimulate perineal region, look for contraction of anus and downward movement of tail

• Cutaneous trunci: pinch skin over epaxial mm, look for bilateral twitch of skin over trunk

where are seizures localized to?

forebrain (ALWAYS)

problem: dull mentation

possible neurolocalization: _______

forebrain or brainstem

problem: circling to the right

possible neurolocalization: ___________

right forebrain or right vestibular

problem: left sided postural reaction deficits

possible neurolocalization: ___________

right forebrain, left brain stem, left spinal cord

What could be the 1 common possibility for neurolocalization of this lesion

Right Forebrain

describe the functions of the forebrain

• alertness

• contralateral processing/interpreting sensory information, decision making

• forming motor plans

• behavior / personality

what makes up the forebrain (2)

cerebrum and diencephalon

what cranial nerves are in the forebrain?

• 1 (olfactory)

• 2 (optic)

describe decerebrate posture

laterally recumbent, extension of head/neck & limbs, stupor to coma, grave prognosis

a patient with a forebrain lesion will circle _____ (toward/away) from the lesion

toward the lesion

name this neurolocalization test

Menace response

name this neurolocalization test

pupillary light reflex

what is the brainstem comprised of? (3)

midbrain, pons, medulla

what are the functions of the brainstem? (list 4 things)

• alertness

• ipsilateral motor pathways

• ipsilateral sensory pathways

• respiration

what cranial nerves are in the brainstem?

-what do these nerves do?

•III, IV, VI Oculomotor, Trochlear, Abducens- ocular and pupil movements

•V Trigeminal- motor to mm. of mastication, sensory to face

•VII Facial- motor to mm. of facial expression, exocrine glands (tears), taste

•VIII Vestibulocochlear- hearing, balance

•IX, X, XII Glossopharyngeal, Vagus, Hypoglossal- tongue movements, gag reflex, taste, PS control of heart and gut, laryngeal function

•XI Spinal accessory “the nerve that got lost”- neck muscles

what are the functions of the cerebellum? (2)

• smooths and fine tunes movement

• coordination and balance

what cranial nerves are in the cerebellum?

none

• however, central portions of vestibular system are in cerebellum (and brainstem)

  • coordination of the blink happens in cerebellum

where does (what portion of the brain) coordination of the blink happen?

cerebellum

describe decerebellate posture.

laterally recumbent, extended head/neck & thoracic limbs, neutral pelvic limbs, normal mentation; prognosis ok

the vestibular system is located within _______

inner ear, brainstem and cerebellum

persistent vertical nystagmus is only seen in _____ (central/peripheral) vestibular lesions

central

Horner’s syndrome is a sign of ______ (centr al/peripheral) vestibular dysfunction

peripheral

is this central or peripheral?

• mentally dull

• listing to the right

• head tilt to the right

• horizontal nystagmus, fp to L

• decreased R facial sensation

*Determine the overall localization

• mentally dull = forebrain or brainstem

• listing to the right = R vestibular, central or peripheral

• head tilt to the right = R vestibular, central or peripheral

• horizontal nystagmus, fast phase to L = R vestibular, central or peripheral

• decreased R facial sensation = Right trigeminal nerve or brainstem

SO overall localization = Right central vestibular

paradoxical vestibular is a subcategory of ______ (central/peripheral) vestibular

central

case: determine the neurolocalization

• dull mentation

• R postural reaction deficits

• L head tilt

• horizontal nystagmus, fast phase R

• dull mentation = Forebrain or brainstem

• R postural reaction deficits = L forebrain, R brainstem or cord

• L head tilt = L vestibular, central or peripheral

• horizontal nystagmus, fast phase R = L vestibular, central or peripheral

• So, overall = Right Paradoxical (central) vestibular