neuroscience block 2

Question 1

Fasciculus gracilis: - all cord levels

Fasciculus cuneatus: only upper thoracic/cervical - upper body correspond (C1–T6)

Answer 1

located between the posterior median sulcus and the posterior intermediate sulcus and septum
found at all cord levels.

Fasciculus cuneatus:
located between the posterior intermediate sulcus and septum and the posterior lateral sulcus
found only at the upper thoracic and cervical cord levels (C1–T6)

Question 2

Lateral funiculus

Anterior funiculus - Contains decussating spinothalamic fibers

Answer 2

located between the posterior lateral and anterior lateral sulci

Anterior funiculus located between the anterior median fissure and the anterior lateral sulcus
contains the anterior white commissure:
Located between the central canal and the anterior medial fissure
Contains decussating spinothalamic fibers

Question 3

Sensory Axons I - IV vs Motor Axons Alpha - Gamma

Answer 3

lower number, A letter - bigger, faster

Question 4

Motor Axons -

alpha and gamma - anterior horn

Alpha extrafusla
Gamma Intrafusal -
preganglionic
post ganglionic

Answer 4

extrafusal fibers vs intrafusual

Extrafusal muscle fibers comprise the bulk of muscle and form the major force-generating structure. Intrafusal muscle fibers are buried in the muscle, and they contain afferent receptors for stretch, but they also contain contractile elements.

Question 5

Sensory I, II, III, IV

Answer 5

IA - propriaception and spindle

IB propriaception and Golgi

II, Touch, pressure Vibe

III, Fast pain, temp, touch, pressure

IV Slow pain, temp, unmylinated

Question 6

Levels of spinal cord, four types of cord

Answer 6

cervical Posterior intermediate sulci and septa
Massive anterior horns (C3-C8)

thoracic - Posterior INTERMEDIATE sulci and septa
Lateral horns

lumbar - Massive anterior and posterior horns
Massive substantia gelatinosa
Lateral horn is prominent at L1

sacral, small - 50 - 50

Coccygeal segment
contains posterior horns that are more voluminous than the anterior horns
has a greatly reduced diameter.

Question 7

Motor Systems

Answer 7

concerned with somatic and visceral motor activities

have their cells of origin in the cerebral cortex or in the brainstem

Question 8

Lateral (Pyramidal)Corticospinal Tract - FINGERS

Decussates in caudal medulla
90% decussation

Answer 8

Function: skilled motor activity
Input: lamina V of motor cortex
Passes through:
Posterior limb of internal capsule
Middle 3/5 of cerebral peduncle
Pyramid of medulla
Decussates in caudal medulla
Runs in posterior part of lateral funiculus
Innervates contralateral extremities

Transection:
Spastic hemiparesis
“+” Babinski sign

Not fully myelinated until the end of the second year
Concerned with volitional skilled motor activity, primarily of the digits of the upper limb
Receives input from the paracentral lobule, a medial continuation of the motor and sensory cortices, and subserves the muscles of the contralateral leg and foot.
Arises from lamina V of the cerebral cortex from three cortical areas: the premotor cortex (area 6); the precentral motor cortex (area 4); and the postcentral sensory cortex (areas 3, 1, and 2)
Terminates via interneurons on anterior horn motor neurons and sensory neurons of the posterior horn
Axons of the giant cells of Betz contribute large diameter fibers to the tract
Passes through the posterior limb of the internal capsule
Passes through the middle three-fifths of the crus cerebri (basis pedunculi) of the midbrain through the base of the pons
Constitutes the pyramid of the medulla
Undergoes a 90% decussation in the caudal medulla
Lies in the posterior quadrant of the lateral funiculus of the spinal cord
Transection results in spastic hemiparesis with positive Babinski sign

Question 9

lesions of corticospinal - upper vs lower motor neurons

upper - if above decussation - contralateral -
below - ipsilateral

lower ipsilateral

Answer 9

upper - spastic

lower - flaccid

If lesions of the corticospinal tract occur above the pyramidal decussation, a weakness is seen in muscles on the contralateral sideof the body; lesions below this level produce an ipsilateral muscle weakness.

In contrast to upper motoneurons, the cell bodies of lower motoneurons are ipsilateral to the skeletal muscles that their axons innervate. A lesion to any part of a lower motoneuron will result in an ipsilateral muscle weakness at the level of the lesion.

Question 10

Rubrospinal - Sit on Rubber mat - anterior to lateral

VIP - STAND - anterior funiculus - Vestibulospinal tract

Answer 10

flexors

Vip - extensors - Vestibular
From ipsilateral lateral vestibular nucleus
Giant cells of Deiters

Question 11

Anterior Corticospinal - AXIAL muscles

that decussates at spinal cord levels in the anterior white commissure

Answer 11

Small uncrossed tract

Innervates axial musculature

Question 12

Tectospinal Tract - head and eye - from hypothalamus down into torso and back to eye

Answer 12

head and eye movement coordinates

The oculosympathetic pathway. Hypothalamic fibers project to the ipsilateral ciliospinal center of the inter- mediolateral cell column at T1. The ciliospinal center projects preganglionic sympathetic fibers to the superior cervical ganglion. The superior cervical ganglion projects perivascular postganglionic sympathetic fibers through the tympanic cavity, cavernous sinus, and superior orbital fissure to the dilator pupillae. Interruption of this pathway at any level results in Horner syndrome. CN 5 cranial nerve.

Question 13

Upper Motor Neurons vs Lower

Answer 13

Cortex and brainstem nuclei (eg, lateral vestibular nucleus, red nucleus)

Lower - Anterior horns of the spinal cord, nuclei of motor CNs (III, IV to VII, IX, X)

Question 14

How voluntary muscles move?

Answer 14

To initiate a voluntary contraction of skeletal muscle, 2 motoneurons, an upper and a lower, must be involved. The upper motoneuron innervates the lower motoneuron, and the lower motoneuron innervates the skeletal muscle.

Most important location of upper motoneurons is in the cerebral cortex. Axons of these cortical neurons course in the corticospinal tract.

Question 15

Lower Motor Neurons and reflexes

Answer 15

2 types of lower motor neurons:
Alpha motor neurons – make skeletal muscles (extrafusal) contract
Gamma motor neurons – make muscle spindles more sensitive to stretch
Both types of LMNs participate in reflexes
Both types of LMNs receive input from UMNs

Question 16

Lower Motor Neuron lesion - flaccid -

Upper - originally flacid, but one week later - spastic

Answer 16

LMN lesion
Flaccid paralysis
Areflexia
Muscle atrophy
Fasciculations and fibrillations

Question 17

skeletal m, two types of innervation

Answer 17

Voluntary innervation (via corticospinal tracts): UMN->LMN

Reflex innervation: muscle sensory neuron
Function of reflex innervation: control of muscle tone

Question 18

M spindles

Answer 18

Motor unit = the basic unit for voluntary, postural, and reflex activity.

Muscle spindle monitor the length and rate of change in length of extrafusal fibers.

Muscles involved with fine movements contain a greater density of spindles than those used in coarse movements.

Question 19

Extrafusal muscle fibers vs intrafusal

Answer 19

Innervated by alpha MN
Fibers innervated by 1 alpha MN = motor unit

Intrafusal muscle fibers
Core of muscle spindle
Muscle spindles act as sensory receptors in stretch reflexes
In parallel with extrafusal f.
Innervated by gamma MN

Question 20

reflexes and lower, upper motor neurons

Answer 20

, lower motoneurons form the specific motor component of skeletal muscle reflexes. Upper motoneurons provide descending control over the reflexes.

Question 21

Muscle stretch (myotatic) reflexes (MSRs)

Muscle tone is the tension present in all resting muscle. Tension is controlled by the stretch reflexes.

Monosynaptic, ipsilateral
Afferent limb: muscle spindle, Ia sensory neuron
Efferent limb: LMN

Answer 21

Contraction of muscle in response to its stretch
Occurs in all muscles
Primary mechanism of muscle tone regulation
Aka deep tendon reflexes (DTRs)

Additional reflexes:
Cremasteric reflex= L1, L2 (“testicles move”)
Anal wink reflex= S3, S4 (“winks galore”)

Question 22

Knee jerk reflex

Answer 22

The best example of a muscle stretch or deep tendon reflex is the knee-jerk reflex. Tapping the patellar ligament stretches the quadriceps muscle and its muscle spindles. Stretch of the spindles activates sensory endings (Ia afferents), and afferent impulses are transmitted to the cord. Some impulses from stretch receptors carried by Ia fibers monosynaptically stimulate the alpha motoneurons that supply the quadriceps. This causes contraction of the muscle and a sudden extension of the leg at the knee. Afferent impulses simultaneously inhibit antagonist muscles through interneurons (in this case, hamstrings).

Question 23

Inverse MSRs

Answer 23

Monitor muscle tension
Use GTOs
↑ force in muscle → ↑ firing rate of Ib afferent neurons (innervate GTOs) → ↑ facilitation of antagonists and inhibition of agonists

GTOs: encapsulated groups of nerve endings that terminate between collagenous tendon fibers at the junction of muscle and tendon, oriented in series with the extrafusal fibers and respond to increases in force or tension generated in that muscle.

Question 24

gamma vs alpha?

Answer 24

Stimulation of gamma MNs → intrafusal fibers contract →

activation of alpha MNs → ↑ muscle tone

Question 25

Flexion withdrawal reflex:

Crossed extension reflex:

Answer 25

Flexion withdrawal reflex:
Protective reflex
Stimulus (usually painful) causes withdrawal of the stimulated limb

Crossed extension reflex:
Accompanies withdrawal reflex
Contralateral limb is extended to help support the body

Question 26

Testing Motor SystemsStrength - 0 total paralysis, 5 normal

Answer 26

0 = total paralysis
1 = contraction visible or felt on palpation
2 = movement in absence of gravity
3 = movement against gravity
4 = full range, but decreased strength
5 = normal strength

Question 27

Testing Motor systems

Answer 27

1. Flaccidmuscle tone indicates an LMN or acute UMN lesion.
2. Increased tone that fades at end of movement(clasp-knife rigidity)indicates a UMN lesion.
3. Increased tone throughout range of movement(lead-pipe or plastic rigidity)indicates basal ganglia disease
   Cog-wheel rigidityproduces ratchet-like catches and releases and accompanies parkinsonism.
4. Decreased tone(hypotonia) withpendular reflexesindicates cerebellar damage

Patients with cerebellar injury may have a knee jerk that swings forwards and backwards several times.

Question 28

Cerebellar damage?

Answer 28

pendular reflex

Question 29

Testing Motor Systems

Testing Motor SystemsDTRs

DTR?

Babinski – indicates corticospinal tract damage - toes FAN instead of curl - = Babinksy= babies have this, but it is normal

Abdominal (T8–T12), cremasteric (L1, L2): absent reflex indicates damaged reflex loop or corticospinal tract damage

Answer 29

Designed to test sensory limb, motor limb, and UMN modulation of muscle stretch reflex

0 = absent
1+, ++ = hypoactive
2+, ++ = normal
3+, +++ = hyperactive
4+, ++++ = clonus present

Question 30

Sensory Neurons

Convey sensory information from the periphery to higher levels

Usually consist of a chain of three neurons:
first-, second-, and third-order neurons

Answer 30

First Order
Second order -
Third

Question 31

First order

Answer 31

always in the spinal ganglion

Question 32

Second Order

Answer 32

always crosses midline

Give rise to collateral branches that serve in local spinal reflex arcs

Question 33

Sensory Receptors -

Free Nerve
Meissner
Pacinian
Merkel
Ruffini

Answer 33

Free Nerve - pain, temp

Question 34

Meissner

Answer 34

hairless skin - glabrous

fine light touch, position sense, dynamic

encapsulated endings found in the dermal papillae of glabrous skin
mediate fine discriminative tactile sensation via the posterior column–medial lemniscus pathway
associated with group II fibers
rapidly adapting

Question 35

Pacinian

Answer 35

deep skin, joints, ligaments

vibration, pressure

found in the dermis, mesenteries, and periosteum
respond to pressure and vibration sensation via the posterior column–medial lemniscus pathway
associated with group II fibers
rapidly adapting

Question 36

Merkel

Answer 36

pressure, edges, finger tips

Non-encapsulated endings found in the basal layer of the epidermis
mediate light (crude) touch (e.g., stroking the skin with a wisp of cotton)
associated with group II fibers
project centrally via the anterolateral system and the posterior column–medial lemniscus pathway
slow-adapting

Question 37

Ruffini

Answer 37

finger tip and joints,

slippage, joint angle change

Question 38

Posterior column medial lemniscus pathway

First-order neurons:
located in spinal ganglia at all levels
give rise to the fasciculus gracilis from the lower extremity
give rise to the fasciculus cuneatus from the upper extremity
give rise to axons that ascend in the posterior columns and terminate in the gracile and cuneate nuclei of the medulla

Second-order neurons:
located in the gracile and cuneate nuclei of the caudal medulla
give rise to axons, internal arcuate fibers that decussate and form a compact fiber bundle, the medial lemniscus
The medial lemniscus ascends through the contralateral brainstem to terminate in the ventral posterolateral (VPL) nucleus of the thalamus

Third-order neurons:
located in the VPL nucleus of the thalamus
project via the posterior limb of the internal capsule to the postcentral gyrus, the somatosensory cortex (areas 3, 1, and 2).

Answer 38

Functions:
Fine (discriminative) touch
Conscious proprioception
Vibratory sense, pressure

Somato-topically organized

Input:
Pacinian and Meissner’s corpuscles
Joint receptors
Muscle spindles
Golgi tendon organs (GTOs)

First order neurons:
Spinal ganglia
Give rise to fasciculi Gracilis (from LE) and Cuneatus (from UE)

Second order neurons:
Caudal medulla (gracile and cuneate nuclei)
Axons cross (internal arcuate fibers) and continue as medial lemniscus

Third order neurons:
VPL nucleus of thalamus
Project to postcentral gyrus

Question 39

Lesions of posterior column medial lemniscuspathway

Answer 39

Signs of lesion:
Loss of tactile discrimination
Loss of position (joint) and vibratory sensation
Stereoanesthesia (astereognosis)
Sensory (posterior column) dystaxia
Paresthesias and pain (posterior root irritation)
Hyporeflexia or areflexia (posterior root deafferentation)
Urinary incontinence, constipation, and impotence (posterior root deafferentation)
Romberg sign (sensory dystaxia) (standing patient is more unsteady with eyes closed)

Question 40

Testing of Posterior Column lesions?

Answer 40

Vibration: tuning fork
The ability to sense vibration diminishes with age
Testing for vibration has limited clinical value in adults > 60 years

Position sense (proprioception):
Awareness of limb position with eyes closed
Romberg sign: loss of position sense and hallmark of posterior column damage
Hold digit (eg., a toe) by sides, not top and bottom, to test position sense

Light touch: wisp of cotton

Question 41

Romberg test - cerebellar prob when AFTER open eyes - inability to stand

Answer 41

1. Patient stands with feet close together and closes eyes.
2. Instability indicatesdecreased proprioceptive senseand is a positive test.
3. Inability to stand with feet together andeyes openindicates cerebellar damage.

Question 42

Anterolateral System - Functions:
Crude touch, itch, PAIN< TEMPERATURE -

ANESTHESIA

neospinothalamic tract

Tract of Lissauer -

Note! The anterolateral system gives projections to reticular formation and intralaminar thalamic nuclei.

Note! Some authors refer to the spinothalamic tracts as two separate tracts. Recently, this concept was replaced with neospinothalamic tract (includes both pathways)

Posterolateral tract (of Lissauer)
(predominantly) white matter tract capping the posterior horn
mainly pain and temperature fibers ascending or descending a few spinal cord segments before synapsing
serves to provide central overlap of pain and temperature

Answer 42

Input:
Free nerve endings
Merkel tactile discs
Thermal receptors

First order neurons:
Dorsal root ganglia at all levels
Project to 2 order neurons via tract of Lissauer

Second order neurons:
Posterior horn
Axons decussate in anterior white commissure
Ascend in contralateral anterior funiculus
Terminate in VPL of thalamus

Third order neurons:
Project to postcentral gyrus via posterior limb of the internal capsule

Question 43

Summary of ascending pain pathways

Answer 43

Pain ascends in all 3 funiculi

Pain in transmitted in the following pathways:

Anterolateral system
Spinoreticular tract
Spinomesencephalic tract
Spinocervical tract

Spinoreticular-ascend as part of the anterolateral system, originate in the contralateral posterior horn, and terminate diffusely throughout the reticular formation; via thalamus projects to all regions of the cortex

Spinomesencephalic-ascend as part of the anterolateral system, originate in the contralateral posterior horn, and terminate on multiple nuclei of the midbrain, projects to PAG (periaqueductal grey), important for emotional response to pain

Spinocervical - travel in the posterior aspect of the lateral funiculus, originate in the nucleus proprius, and terminate in the cervical spinal cord

Question 44

Cordotomy Surgical sectioning of spinothalamic tract

Answer 44

Provides immediate relief of intractable pain (eg, from pancreatic cancer)

Pain usually returns after several months
Reasons are unknown
Uncrossed spinothalamic/spinomesencephalic fibers may contribute to return of pain
Some pain input may be carried through posterior column system

Neuropathic pain may be major source of returning pain

Question 45

Neuropathic pain

Answer 45

is pain caused by damage or disease affecting the somatosensory nervous system. Neuropathic pain may be associated with abnormal sensations called dysesthesia or pain from normally non-painful stimuli (allodynia). It may have continuous and/or episodic (paroxysmal) components.

Question 46

Testing anterolateral system

Answer 46

Pain: pinprick
Temperature: warm and cold vials

Question 47

Cerebellar tracts

Posterior spinocerebellar tract contains axons that terminate ipsilaterally as mossy fibers in the cortex of the rostral and caudal cerebellar vermis.

Answer 47

. Posterior spinocerebellar tract:
Function:
Unconscious proprioception
Coordination of posture
Fine movements of LE
Input: muscle spindles, GTOs, pressure receptors
Uncrossed

First-order neurons:
Spinal ganglia C8-S3

Second-order neurons:
Posterior thoracic nucleus (C8-L3)
Ascends in lateral funiculus
Reach cerebellum via inferior cerebellar peduncle

Question 48

Cuneocerebellar tract:

UE equivalent of posterior spinocerebellar tract

Answer 48

First-order neurons:
Spinal ganglia C2-T7
Axons project via fasciculus cuneatus

Second-order neurons:
Accessory cuneate nucleus (homolog of the posterior thoracic nucleus)
Project to ipsilateral part of the cerebellum (inf. cerebellar peduncle)

Question 49

. Anterior spinocerebellar tract:

INHERITED - Ataxia of GAIT -

Function:
Unconscious proprioception
Coordination of posture of LE
Input: muscle spindles, GTOs, pressure receptors
Crossed

Lesions that affect only the spinocerebellar tracts are uncommon, but there are a group of hereditary diseases in which degeneration of spinocerebellar pathways is a prominent feature. The most common of these is Friedreich ataxia, which is usually inherited as an autosomal recessive trait. The spinocerebellar tracts, dorsal columns, corticospinal tracts, and cerebellum may be involved. Ataxia of gait is the most common initial symptom of this disease.

Answer 49

First-order neurons:
Spinal ganglia L1-S2

Second-order neurons:
Spinal border cells L1-S2
Ascends in lateral funiculus
Reach contralateral cerebellum via superior cerebellar peduncle

Question 50

hyperreflexia vs hyproreflexia

Lower - Motor Neurons - Hyporeflexia refers to a condition in which your muscles are less responsive to stimuli. If your muscles don’t respond at all to stimuli, this is known as areflexia. Your muscles may be so weak that you can’t do everyday activities.

Answer 50

Hyperreflexia is defined as overactive or overresponsive reflexes. Examples of this can include twitching or spastic tendencies, which are indicative of upper motor neuron disease as well as the lessening or loss of control ordinarily exerted by higher brain centers of lower neural pathways (disinhibition).

Question 51

Hypertonia (UMN) vs hypo (lower)

Answer 51

is a condition in which there is too much muscle tone so that arms or legs, for example, are stiff and difficult to move. Muscle tone is regulated by signals that travel from the brain to the nerves and tell the muscle to contract.

Question 52

upper vs lower neuron signs

Lower - hyporeflexia, hypotonia, flaccid, fasciculations (twitching as lose innervation)

thought to be caused by release of acetylcholine from the degenerating nerve terminal at the neuromuscular junction.

Answer 52

upper - spastic, clasp knife rigidity, babinski (fanning after 1yo), clonus

Clonus is a type of neurological condition that creates involuntary muscle contractions. This results in uncontrollable, rhythmic, shaking movements. People who experience clonus report repeated contractions that occur rapidly.

Question 53

Hypoperfusion of the anterior spinal artery

The anterior (ventral) spinal artery (ASA) ( ventral cord) relies on only one artery, making it more vulnerable to infarction than the posterior cord.

Answer 53

Occlusion or hypoperfusion of the anterior spinal artery results in weakness below the level of occlusion, loss of pain, and temperature at or below the level because of involvement of the lateral spinothalamic tracts, and autonomic dysfunction such as loss of bowel and bladder function.

Although the blood supply to the spinal cord is considered rich, the spinal canal is narrowest—and the blood supply is poorest—at T4-9. This is why it is deemed the critical vascular zone of the spinal cord, since interference with circulation is most likely to result in paraplegia. The upper thoracic ASA territory is considered a watershed area, with the artery of Adamkiewicz being one of the largest radicular arteries supplying the ASA.

It causes bilateral deficits below the lesion affecting:

Pain and temperature sensation (spinothalamic tract)

Voluntary motor control (lateral corticospinal tract)

Autonomic motor control (including bladder and bowel control)

However, the dorsal columns (light touch, vibration, proprioception) are spared. This patient most likely had an anterior cord infarction at the level of T4 during a period of hemodynamic instability requiring transfusions.

Question 54

Anterior spinal artery syndrome - often after surgery - esp if lose blood

Answer 54

can affect all ascending and descending pathways except for the dorsal columns, which are located in the most posterior aspect of the spinal cord. Because the dorsal columns are used for proprioception and vibration, these functions should remain intact, whereas all others (pain, temperature, motor functions) should be decreased. This patient would then experience decreased pain sensation and normal vibration sense.

Question 55

The dorsal column–medial lemniscus pathway (DCML)

The dorsal column includes the fasciculus cuneatus and fasciculus gracilis, each of which contain sensory neurons involved in pressure, vibration, fine touch, and proprioception.

Answer 55

(also known as the posterior column-medial lemniscus pathway, PCML) is a sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point discrimination, and proprioception (position) from the skin and joints.

Question 56

What is the function of the lateral corticospinal tract?

most muscles

Answer 56

The lateral corticospinal tract contains over 90% of the fibers present in the corticospinal tract and runs the length of the spinal cord. The primary responsibility of the lateral corticospinal tract is to control the voluntary movement of contralateral limbs.

Question 57

anterior corticospinal tract - trunk muscles - don’t decussate

Answer 57

do not decussate in the pyramidal decussation and instead continue down to the spinal cord on the ipsilateral side of the brainstem from where they originated. The anterior corticospinal tract is involved in controlling proximal muscles, like those of the trunk.

Question 58

The lateral spinothalamic tract, - PAIN, TEMP

Ascending

Answer 58

also known as the lateral spinothalamic fasciculus, is an ascending pathway located anterolaterally within the peripheral white matter of the spinal cord. It is primarily responsible for transmitting pain and temperature as well as coarse touch.

Question 59

anterior spinothalamic tract, COURSE touch and pressure

Ascending

Answer 59

also known as the ventral spinothalamic fasciculus, is an ascending pathway located anteriorly within the spinal cord, primarily responsible for transmitting coarse touch and pressure.

Question 60

1 mo old - difficulty with feedings and has noticed that he cannot keep his head supported while in the prone position. On examination, you notice the boy has a weak cry and difficulty maintaining posture. The infant also has generalized muscle atrophy and reduced ankle and brachial reflexes.

Answer 60

Anterior horn of spinal cord

This patient presents with difficulty maintaining posture and head support, diminished deep tendon reflexes, and weak cry, all of which suggest a lower motor neuron (LMN) lesion. This patient most likely has spinal muscular atrophy (SMA) type 1, also known as Werdnig-Hoffmann disease, which is characterized by destruction of the anterior horn cells of the spinal cord. SMA is due to an autosomal recessive mutation in the SMN1 gene (survival motor neuron) that is thought to play a role in mRNA synthesis in motor neurons and inhibition of apoptosis. This condition affects only the LMN system, which includes the anterior horn cells of the spinal cord, ventral nerve root, peripheral nerve, neuromuscular junction, and skeletal muscle. Patients with LMN disease will experience muscle atrophy, proximal muscle weakness, fasciculations, hypotonia, and diminished deep tendon reflexes. Poliomyelitis infection could also cause isolated LMN disease.

Question 61

polio - lack of vaccine - intl travel

Answer 61

Neuron loss in the anterior horns

Poliovirus is passed by the fecal-oral route and initially infects the Peyer patches of the intestine and motor neurons. The disease can manifest with a spectrum of severity, as noted in the table. Replication of poliovirus in motor neurons of the anterior horn of the spinal cord results in cell destruction, which leads to the neurologic sequelae of poliomyelitis. There is no cure for polio and treatment is aimed at preventing complications, including paralysis, hypotonia, and hyperreflexia.

Question 62

ALS - Anterior horn and lateral column degeneration with gliosis

Patient has long-term history of muscle weakness within his lower extremities, which has confined him to a wheelchair. His other symptoms, including dysarthria, tongue fasciculations, dysphagia, and extensor plantar responses, support a diagnosis of amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig disease. ALS usually begins in middle age and progresses to death over a period of a few years

Answer 62

is characterized by the atrophy of the anterior horn cells and replacement of the large motor neurons by fibrous astrocytes (gliosis), which causes the affected anterior and lateral columns of the spinal cord to become hard (lateral sclerosis).

ALS is characterized by the atrophy of the anterior horn cells and replacement of the large motor neurons by fibrous astrocytes (gliosis), which causes the affected anterior and lateral columns of the spinal cord to become hard (lateral sclerosis). This degenerative process is marked by the loss of upper and lower motor neurons, with sparing of sensory and autonomic neurons. The degeneration of the anterior horn results in progressive weakness that proceeds from neurogenic muscular atrophy to paralysis. The skeletal muscle fibers appear small and angular due to denervation atrophy. In this scenario, the patient developed lower motor neuron signs of weakness, atrophy, and fasciculations. Loss of neurons in the nuclei of cranial nerves V, IX, X, and XII can also be present, resulting in bulbar signs (dysarthria, dysphagia) from the lower motor neuron lesion.

The patient also has a positive Babinski reflex (extensor plantar response), which is indicative of upper motor neuron lesions. Upper motor neuron signs are due to degeneration of the lateral corticospinal tract and mild atrophy of the prefrontal gyrus. Patients usually retain mental function over the course of the disease, and death is usually caused by paralysis of respiratory muscles.

Question 63

A whorled pattern of concentrically arranged spindle cells

meningioma

Answer 63

within the meninges describes the classic microscopic appearance of a meningioma. These neoplasms are slow growing and resectable, but may reach a large size before symptoms such as headaches and blurry vision lead to detection.

Question 64

vegan, weak, unsteady, falling, b12 deficiency

Which of the following CNS regions is most likely abnormal in this patient?

Dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts

Answer 64

The most prominent findings in vitamin B12 deficiency are glossitis (large, shiny tongue), macrocytic megaloblastic anemia with hypersegmentedneutrophils, and neurologic findings including dementia-like symptoms and ataxia. These neurologic findings are due to the degeneration of neurons and myelin in the dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts (red arrow), indicative of B12 deficiency.

Question 65

tertiary syphilis.

Answer 65

The dorsal column and dorsal roots are affected in tabes dorsalis caused by

Question 66

ALS

Answer 66

Degeneration of the ventral horn, precentral gyrus, and lateral corticospinal tract is seen in patients with amyotrophic lateral sclerosis.

Question 67

syringomyelia

Answer 67

The anterior white commissure is affected in syringomyelia, in which a syrinx develops within the central canal of the spinal cord, typically at C8-T1 levels.

Question 68

MS

Answer 68

The medial longitudinal fasciculus and periventricular white matter area are commonly involved in multiple sclerosis.

Question 69

Vestibulospinal tracts VIP - stand - extesors

Answer 69

The descending tracts that originate from the vestibular nuclei of the brainstem. They consist of a medial tract and a lateral tract. The medial vestibulospinal tract arises from the medial vestibular nucleus. It descends on the ipsilateral side of the spinal cord.

Question 70

The spinocerebellar tracts

Answer 70

are afferent neurons that convey proprioceptive data from the spinal cord to the cerebellum. There are anterior (or Gowers’ tract) and posterior spinocerebellar tracts, the latter also referred to as Flechsig’s tract.

Question 71

two eyes can’t move together? MS

Answer 71

Lesion - Medial longitudinal fasciculus

MS is a chronic neurologic disorder affecting the white matter of the central nervous system (CNS). This disease typically affects young women (20–30 years old) and commonly manifests first with ocular problems. Other symptoms include unilateral optic neuritis, cerebellar dysfunction (ataxia, nystagmus, vertigo), bowel and bladder dysfunction, tingling or numbness, and muscle weakness. These symptoms can be exacerbated by heat since it slows the rate of conduction through demyelinated nerves even more, which explains why this patient experienced worsening weakness and fatigue after being in a sauna (Uhthoff phenomenon).

When a healthy patient gazes to one side, lower motor neurons in the abducens nucleus send fibers via CN VI to the ipsilateral lateral rectus muscle, causing the ipsilateral eye to abduct. Simultaneously, interneurons in the abducens nucleus send their fibers across the midline to enter the contralateral medial longitudinal fasciculus (MLF) and synapse on neurons in the oculomotor nucleus that innervate the medial rectus muscle and cause the opposite eye to adduct. Through this mechanism, both eyes move conjugately in the horizontal plane. In MS, demyelination of the MLF secondary to the underlying disease process results in the failure of either eye to abduct on attempted horizontal gaze.

The contralateral abducting eye may demonstrate a horizontal nystagmus. The underlying mechanism for the nystagmus is uncertain, but it may be explained by the Heringlaw of equal innervation, which states that conjugate eye movements occur because yoke muscles (eg, the medial and lateral recti for horizontal eye movements) receive equal and simultaneous innervation. In INO, attempts to increase innervation to the weak medial rectus muscle are accompanied by a commensurate increase in innervation to its yoke muscle (the contralateral lateral rectus), producing nystagmus.

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The Edinger-Westphal nucleus

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supplies parasympathetic innervation to the pupil and ciliary muscle, but not to the somatic fibers involved in ocular movement.

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The arcuate fasciculus

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connects the Broca and Wernicke language areas in the dominant (usually left) hemisphere. Damage results in a language impairment known as conduction aphasia.

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The medial lemniscus is a brainstem fiber pathway

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that carries somatosensory information from the extremities to the brain. Lesions here produce a loss of fine touch, conscious proprioception, and vibratory sense from the contralateral side of the body.

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Frontal Eye Field

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The frontal eye field (FEF) is located near the intersection of the middle frontal gyrus with the precentral gyrus. Irritative lesions to the FEF (eg, seizure) cause horizontal conjugate deviation of the eyes away from the lesion, whereas destructive lesions of the FEF (eg, stroke) produce horizontal conjugate gaze toward the side of the lesion

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The dorsal root ganglion is damaged in Charcot-Marie-Tooth syndrome,

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which manifests as a loss of limb sensation.

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Damage to the dorsal columns results from syphilis and vitamin B12 deficiency,

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which manifests with proprioceptive and vibratory sensation abnormalities.

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Ventral horn damag

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e can occur from poliomyelitis and ALS and results in motor damage rather than sensory impairment.

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Chiari I malformation,

Spinothalamic tract

frequent headaches that worsen when she bends over.

lost some sensation in both of her hands,

Show CT

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which is an anatomic abnormality characterized by displacement of the cerebellar tonsils below the level of the foramen magnum. A common manifestation of Chiari I malformation is elevated intracranial pressure, which would explain this woman’s position-dependent headaches.

Chiari I malformations are often associated with syringomyelia, a disorder caused by a cystic cavity (syrinx) inside the spinal cord which most commonly affects the C8–T1 level. The syrinx can impinge upon fibers of the spinothalamic tract as they cross through the anterior white commissure, located medially and anterior to the center of the spinal cord. Involvement of the spinothalamic tract results in bilateral loss of pain and temperature sensation, usually seen in the upper extremities (with a syrinx located around C8–T1).

Question 80

Anterior horn problem - polio

anterior white commissure - syringomyelia.

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Degeneration of the posterior columns and corticospinal characteristic of pernicious anemia (vitamin B12 deficiency).

Degeneration of the posterior column is a classic finding in tertiary syphilis.

Question 81

A 63-year-old man undergoes surgery to remove a benign tumor in the spinal canal. As a result of the surgery, there is damage to fasciculus gracilis on the right side at T7-T10. Following recovery, he has a limited neurologic deficit due to this damage. Which of the following is most likely given these findings?

. Decreased pain sensation from the right leg Incorrect

b. Decreased proprioceptive sensation from the right leg
c. Dysmetria in the left arm
d. Dysmetria in the right arm
e. Decreased pain sensation from the left leg
f. Decreased proprioceptive sensation from the left leg

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Fasciculus gracilis, within the posterior columns, carries fine touch, proprioception, and vibration sensation from the ipsilateral lower body and leg (starting at about T6).

The correct answer is: Decreased proprioceptive sensation from the right leg

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C5 - C6` - elbow

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elbow
c 4, c5 shoulder

c7 - 8 triceps
c 5 - 6 biceps

c8 - wrist flexion

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L4

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patellar reflex

S1 - Achilles

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lateral pontine syndrome

cause: infarct of circumferential branches of the basilar and anterior inferior cerebellar (AICA) arteries.

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ipsilateral loss of pain/temperature sensation from the face and contralateral loss of pain/temperature sensation from the trunk and extremities

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Wallenberg syndrome vs Lateral Pontine?

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Lateral Pontine is similar to lateral medullary syndrome (Wallenberg syndrome) except that it also involves the trigeminal nucleus.

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most common brain stem stroke? LEFT MEDULLA if LEFT FACE< right body

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wallenburg - sudden onset hoarseness, dysphagia, ataxia, and alternating hemianalgesia (diminished pain/temperature sensation of the ipsilateral face and contralateral body)

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Hoarseness (or dysphagia)?

Lateral medulla has most likely been affected by dissection or thrombosis of the vertebral artery, which gives rise to the posterior inferior cerebellar artery (PICA). The PICA supplies blood to structures of the lateral medulla (vestibular nuclei, spinal cord tracts) and the inferior cerebellar peduncle.

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if present) is fairly specific for lateral medullary syndrome (Wallenberg syndrome) because it points to a lesion of the nucleus ambiguus (CN IX, X, XI)

expect also to see ptosis and miosis

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paralysis and loss of vibratory sensation and proprioception on the right side

“a funny feeling” in her right arm and leg.

her tongue deviates to the left

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Anterior spinal artery

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The patient’s symptoms of headache, nausea, and vomiting combined with a fundus photo depicting swelling of the optic nerve head (papilledema), are strongly suggestive of

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increased intracranial pressure (ICP).

pineal mass