Neuroexam Neuroanatomy Flashcards
Describe alexia without agraphia:
- as a syndrome and
- in terms of localization
Alexia without agraphia is a syndrome of being UNable to read but being ABLE to write and it typically is associated with right homonymous hemianopia and localizes to the left occipital lobe + splenium
Because the left occipital lobe is involved, there is no input from the right visual fields
Input from the left visual fields travels to the right visual cortex (occipital lobe) but cannot be transmitted to the dominant hemisphere to send to the angular gyrus (reading center) due to splenium involvement
Patients will be unable to read but able to write and have intact comprehension and speech
Describe Gerstmann’s syndrome
Impairment of four features caused by lesions in dominant parietal lobe (may be seen with aphasia and thus very difficult or impossible to diagnose)
- Acalculia
- Right-left confusion
- Finger agnosia
- Agraphia
Describe the common types of apraxia
Ideomotor apraxia - most common type, describes when despite having all of the functions to be able to perform or demonstrate a motor dask, cannot do so (ie show how to use a toothbrush, strike a match and blow it out)
Ideational apraxia - cannot perform previously learned complex task in the correct sequence (ie putting on shoes before socks)
Conceptual apraxia - similar to ideomotor apraxia but actually doesn’t use a tool correctly (ie someone using screwdriver as a pen)
Constructional apraxia - can’t draw, construct, or copy
Frontal lobe exam maneuvers
Sequencing tasks - ie drawing a series of square/triangles and patients demonstrating PERSEVERATION ie getting stuck on one object and drawing it
Luria manual sequencing task - tap table with fist, open palm, and side of open hand
Motor impersistence - distractibility in which patients only briefly sustain a motor action in response to a command such as “raise your arms” or “look to the right”
Auditory go-no-go test - hit hand in response to only “A” in a series of leters
Frontal release signs - ie grasp reflex
Abulia - slow responses or change in personality and judgement
Frontal release signs aka “primitive” reflexes
Suck reflex - lightly touching the lips with an object results in sucking movements of the lips
Snout reflex - tapping upper lip will cause contraction of muscles causing mouth to resemble snout
Palmomental reflex - stimulus from thenar eminance to the base of the thumb resulting in ipsilateral contraction of orbicularis oris and mentalis muscle, corner of chin elevates slightly and skin over chin wrinkles
Grasp reflex - examiner’s hand inserted into palm of patient’s hand (distraction useful) and light touch/stimulus in distal direction causing patient to grasp examiner’s hand and continues to grasp as examiner’s hand removed, ability to release voluntarily depends on activity of the reflex
Grasp reflex more specifically related to disease of supplementary motor area of the frontal lobe
https://www.ncbi.nlm.nih.gov/books/NBK395/
Describe the 2 level mechanism by which eye movement disorders can be broken into
- Nuclear and infranuclear pathways - brainstem nuclei and peripheral nerves arising from these nuclei (III, IV, VI)
- Supranuclear pathways - brainstem and forebrain circuits that control eye movements through connections with the nuclei of CN III, IV, VI
Describe the extraocular muscles and function
6 muscles for each eye:
Superior rectus - elevation (and intorsion when eyes directed forward and even more so when adducted; pure elevation when abducted)
Inferior rectus - depression (and extorsion)
Medial rectus - adduction
Lateral rectus - abduction
Superior oblique - passes through the trochlea to produce intorsion (also causes depression when eye is adducted and thus more in line with angle of eye)
Inferior oblique - originates at anterior medial orbital wall and insters on inferior surface of the eye to produce extorsion (also causes elevation especially when eye is adducted)
Fill out this diagram
And…explain relevance of the angle between the plane of gaze and muscle body contributes to eye movements
Some of these notes are not that helpful
Blumenfeld has a great description, I think the best way to think of it is comparing the plane of gaze to that of the EOM mucle body in question and working from SR first is probably best because you can logic through the rest
With forward gaze, the direction of pupils is ~23 degrees off from the plane of the SR muscle which is lateral to the pupils on both sides. That means with forward gaze, contraction of SR will cause not just elevation but INTORSION. With lateral gaze ie to the left, the abducted eye will move into closer parallel with muscle body (ie left eye) so action on that eye will be PURE elevation while the other eye will have moved further away from the plane of the muscle body of SR so there will be MORE intorsion.
Describe the somatic motor column of nuclei and characteristics
CN III
CN IV
CN VI
CN XII
- Lie near midline, adjacent to ventricular system, fibers exit brainstem ventrally near the midline with the exception of CN IV (trochlear) which exits dorsally
What is unique about course of CN IV (trochlear)? What type of injury are they susceptible to?
They decussate BEFORE leaving the DORSAL aspect of the inferior midbrain (at the level of inferior colliculi)
Because they exit dorsally they are at high risk of compression from CEREBELLAR tumors
They are extremely thin and friable and can be damanged by shear injury from head trauma
Also susceptible to damage in subarachnoid space and cavernous sinus
What is special about trajectory of CN VI (abducens) nerve? Where is it most susceptible to injury?
Nuclei lie under facial colliculi at the floor of the 4th ventricle, it exits at mid-to-lower pons (travels ventrally to exit at pontomedullary junction)
It has a very long course in subarachnoid space between pons and clivus
Exits the dura to enter Dorello’s canal between the dura and the skull under petroclinoid ligament and then makes a sharp bend over the petrous tip of the temporal bone to reach cavernous sinus
Long vertical course - why the abducens nerve is highly susceptible to downward traction injury produced by elevated ICP
What is the hung up reflex?
Hung-up knee jerk (segment 1) is a rare sign caused by delayed relaxation of the quadriceps femoris muscle during deep tendon reflex assessment.
The hung-up reflex has been classically described in hypothyroidism and Huntington disease,1 and this case suggests that it may also be a feature of stiff person syndrome
