Neuroanatomy & Neurologic Examination Flashcards
What is the difference between UMN and LMN?
UMN = brain stem neurons that send axons down the spinal cord to “tell” LMN what to do
LMN = neurons directly innervating muscles that are required to so come action once the UMN directs them
What is the difference between UMN and LMN paresis?
UMN = “release” phenomenon where muscles become rigid and reflexes increase (spastic)
LMN = flaccid paresis with muscle atrophy
UMN vs LMN signs:
What are stepping centers? What 2 things do they require for function?
neuronal circuits within the spinal cord that can generate stepping movements
- stimulus, normally from a brainstem motor tract
- purposefulness of movement from cerebrum
What are 3 major clinically relevant components of the brain?
- forebrain - cerebrum, diencephalon
- brainstem - midbrain to medulla
- cerebellum
What is the function of the cerebrum? How are the modalities represented?
sensory phenomena terminate here for processing —> corticospinal motor tracts are of little significance
contralaterally
What serves as the relay center for sensory input in the cerebrum?
diencephalon
What are the 5 clinical features of forebrain dysfunction?
- abnormal mental status, usually obtunded
- seizures
- proprioceptive placing deficits with normal to near-normal gait
- visual deficits contralateral to lesion side
- decreased facial sensation contralateral to lesion
What are the 6 major physical exam findings in patients with forebrain dysfunction?
- circling, usually wide and in the direction of the lesion
- head and neck pain on palpation
- mild anisocoria contralateral to lesion
- mild facial paralysis contralateral to lesion
- hemineglect, hemi-inattention
- head turn
What is hemineglect (hemi-inattention) syndrome?
evident with lateralized forebrain tumors, where there is…
- head turn and circle to the side of the lesion (ignoring the other side)
- difficulty responding to auditory stimuli, nociceptive stimuli, and food/treats on the inattentive side
What are the 2 major functions of the diencephalon?
- thalamus acts as relay station
- hypothalamus acts as a hormonal center for ANS control
What 3 aspects of the nervous system does the thalamus have control of?
- vision - lateral geniculate nucleus
- hearing - medial geniculate nucleus
- proprioception, nociception - VCT nucleus
What’s the difference between conscious and unconscious proprioception?
CONSCIOUS - sense of limb movement and static limb position in space, forebrain
UNCONSCIOUS - arises from resting muscle tension and stretch, cerebellar
12 y/o MC Staffordshire - Acute onset of circling and behavior change. There is also decreased proprioceptive positioning and menace reaction on the right side. Where is the lesion most likely located?
left forebrain
- conscious proprioception = forebrain
- right-sided hemineglect = left (forebrain)
What are the 3 major manifestations of hypothalamic lesions?
- endocrine disorders
- temperature regulation problems
- changes in appetite
What is the main function of the basal nuclei? What are the 3 structures found here?
modulates stereotypic motor movements and activity —> likely source of movement disorders
- caudate nucleus
- putamen
- globus pallidus
What is the source of all seizures?
forebrain
What is the hallmark of forebrain lesions? What else is commonly seen?
normal to near-normal gait (often circling) with decreased contralateral proprioceptions
behavior changes
What are 4 clinical manifestations associated with brainstem dysfunction?
- more obvious gait abnormalities
- central vestibular dysfunction
- abnormal mentation
- pharyngeal dysfunction
What are the 2 hallmarks of brainstem dysfunction? What important nerves are found here?
- gait and proprioceptive dysfunction ipsilateral to lesion
- central vestibular manifestations
cranial nerve nuclei of III-XII
What are the 3 gait-generating nuclei in the brainstem?
- red nucleus - rubrospinal tract in midbrain
- pontine reticular formation - pons to spinal tract
- medullary reticular formation - medullat to spinal tract
What 4 important nervous structures are found in the mesencephalon (midbrain)? What function do they have?
- red nucleus and rubrospinal tract - gait
- oculomotor nucleus (III) - eye movement and pupil constriction
- beginning of the sympathetic tract to the eye
- part of the ascending reticular activating system - arouse the cerebral cortex, awaken the brain to a conscious level, and prepare the cortex to receive the rostrally projecting impulses from any sensory modality
What makes up the ventral metencephalon? What 4 important nervous structures are found here?
pons
- pontine reticulospinal tract - gait
- trigeminal nucleus (V) - masticatory muscles, sensory
- part of ARAS
- pneumotaxic center - I:E ratio
Where does information from the sensory tract of the trigeminal nucleus (V) go?
crosses to the opposite cerebrum
- not localizing by itself
What makes up the myelencephalon? What are 5 important nervous systems found here?
medulla oblongata
- medullary reticulospinal tract - gait
- cranial nerve nuclei VI-XII
- part of ARAS
- major cardiac and respiratory centers
- major control centers of BP
What are the major functions of the nucleus ambiguus and CNs IX, X, and XI?
laryngeal, pharyngeal, and esophageal function
How do patients with central vestibular dysfunction typically present?
- usually non-ambulatory
- slow or inapparent spontaneous nystagmus
What is the function of the cerebellum? How does it function?
uses incoming information to modify outgoing responses to smooth out movement
inhibits excitatory neurons