Neurology - Anatomy and Physiology (3) Flashcards
1
Q
Dorsal column
- Function
- 1st-order neuron
- Synapse 1
- 2nd-order neuron
- Synapse 2
- 3rd-order neuron
A
- Function
- Ascending
- Ascending tracts synapse and then cross.
- Pressure, vibration, fine touch, and proprioception
- Ascending
- 1st-order neuron
- Sensory nerve ending
- –> cell body in dorsal root ganglion
- –> enters spinal cord, ascends ipsilaterally in dorsal column
- Synapse 1
- Ipsilateral nucleus cuneatus or gracilis (medulla)
- 2nd-order neuron
- Decussates in medulla
- –> ascends contralaterally in medial lemniscus
- Synapse 2
- VPL (thalamus)
- 3rd-order neuron
- Sensory cortex
2
Q
Spinothalamic tract
- Function
- 1st-order neuron
- Synapse 1
- 2nd-order neuron
- Synapse 2
- 3rd-order neuron
A
- Function
- Ascending
- Ascending tracts synapse and then cross.
- Lateral: pain, temperature
- Anterior: crude touch, pressure
- Ascending
- 1st-order neuron
- Sensory nerve ending (Aδ and C fibers) (cell body in dorsal root ganglion)
- –> enters spinal cord
- Synapse 1
- Ipsilateral gray matter (spinal cord)
- 2nd-order neuron
- Decussates at anterior white commissure
- –> ascends contralaterally
- Synapse 2
- VPL (thalamus)
- 3rd-order neuron
- Sensory cortex
3
Q
Lateral corticospinal tract
- Function
- 1st-order neuron
- Synapse 1
- 2nd-order neuron
- Synapse 2
A
- Function
- Descending
- Voluntary movement of contralateral limbs
- 1st-order neuron
- UMN: cell body in 1° motor cortex
- –> descends ipsilaterally (through internal capsule), most fibers decussate at caudal medulla (pyramidal decussation)
- –> descends contralaterally
- Synapse 1
- Cell body of anterior horn (spinal cord)
- 2nd-order neuron
- LMN: leaves spinal cord
- Synapse 2
- NMJ
4
Q
Motor neuron signs
- Lower MN
- Upper MN
- Fasciculations
- Positive Babinski
- For each(+/-)
- UMN lesion
- LMN lesion
- Weakness
- Atrophy
- Fasciculations
- Reflexes
- Tone
- Babinski
- Spastic paralysis
- Flaccid paralysis
- Clasp knife spasticity
A
-
Lower MN
- Everything lowered (less muscle mass, decreased muscle tone, decreased reflexes, downgoing toes).
-
Upper MN
- Everything up (tone, DTRs, toes).
- Fasciculations
- Muscle twitching.
- Positive Babinski
- Normal in infants.
- Weakness
- UMN lesion: +
- LMN lesion: +
- Atrophy
- UMN lesion: -
- LMN lesion: +
- Fasciculations
- UMN lesion: -
- LMN lesion: +
- Reflexes
- UMN lesion: Increased
- LMN lesion: Decreased
- Tone
- UMN lesion: Increased
- LMN lesion: Decreased
- Babinski
- UMN lesion: +
- LMN lesion: -
- Spastic paralysis
- UMN lesion: +
- LMN lesion: -
- Flaccid paralysis
- UMN lesion: -
- LMN lesion: +
- Clasp knife spasticity
- UMN lesion: +
- LMN lesion: -
5
Q
Spinal cord lesions:
Poliomyelitis and spinal muscular atrophy (Werdnig-Hoffmann disease)
A
- LMN lesions only
- Due to destruction of anterior horns
- Flaccid paralysis.
6
Q
Spinal cord lesions:
Multiple sclerosis
A
- Due to demyelination
- Mostly white matter of cervical region
- Random and asymmetric lesions, due to demyelination
- Scanning speech, intention tremor, nystagmus.
7
Q
Spinal cord lesions:
Amyotrophic lateral sclerosis
- Definition
- Findings
- Treatment
A
- Definition
- Combined UMN and LMN deficits with no sensory, cognitive, or oculomotor deficits
- Both UMN and LMN signs.
- Can be caused by defect in superoxide dismutase 1.
- Commonly known as Lou Gehrig disease
- Stephen Hawking is a well-known patient who highlights the lack of cognitive deficit
- Combined UMN and LMN deficits with no sensory, cognitive, or oculomotor deficits
- Findings
- Commonly presents as fasciculations with eventual atrophy and weakness of hands
- Fatal
- Treatment
- Riluzole treatment modestly increased survival by decreased presynaptic glutamate release.
- For Lou Gehrig disease, give rilouzole
8
Q
Spinal cord lesions:
Complete occlusion of anterior spinal artery
A
- Spares dorsal columns and Lissauer tract
- Upper thoracic ASA territory is a watershed area, as artery of Adamkiewicz supplies ASA below ~T8.
9
Q
Spinal cord lesions:
Tabes dorsalis
- Due to…
- Associated with…
- Exam
A
- Due to…
- Caused by 3° syphilis.
- Results from degeneration (demyelination) of dorsal columns and roots –> impaired sensation and proprioception and progressive sensory ataxia (inability to sense or feel the legs –> poor coordination).
- Associated with…
- Charcot joints, shooting pain, Argyll Robertson pupils (small bilateral pupils that further constrict to accommodation and convergence, not to light).
- Exam
- Will demonstrate absence of DTRs and (+) Romberg.
10
Q
Spinal cord lesions:
Syringomyelia
A
- Syrinx expands and damages anterior white commissure of spinothalamic tract (2nd-order neurons)
- –> bilateral loss of pain and temperature sensation (usually C8–T1)
- Seen with Chiari I malformation
- Can expand and affect other tracts.
11
Q
Spinal cord lesions:
Vitamin B12 or vitamin E deficiency
A
- Subacute combined degeneration
- Demyelination of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts
- Ataxic gait, paresthesia, impaired position and vibration sense.
12
Q
Poliomyelitis
- Definition
- Symptoms
- Findings
A
- Definition
- Caused by poliovirus (fecal-oral transmission).
- Replicates in the oropharynx and small intestine before spreading via the bloodstream to the CNS.
- Infection causes destruction of cells in anterior horn of spinal cord (LMN death).
- Symptoms
- LMN lesion signs—weakness, hypotonia, flaccid paralysis, fasciculations, hyporeflexia, and muscle atrophy.
- Signs of infection—malaise, headache, fever, nausea, etc.
- Findings
- CSF with increased WBCs and slight increase of protein (with no change in CSF glucose).
- Virus recovered from stool or throat.
13
Q
Spinal muscular atrophy (Werdnig-Hoffmann disease)
A
- Congenital degeneration of anterior horns of spinal cord –> LMN lesion.
- “Floppy baby” with marked hypotonia and tongue fasciculations.
- Infantile type has median age of death of 7 months.
- Autosomal recessive inheritance.
14
Q
Friedreich ataxia
- Definition
- Findings
A
- Definition
- Autosomal recessive trinucleotide repeat disorder (GAA) on chromosome 9 in gene that encodes frataxin (iron binding protein).
- Leads to impairment in mitochondrial functioning.
- Findings
- Presents in childhood with kyphoscoliosis
- Degeneration of multiple spinal cord tracts –> muscle weakness and loss of DTRs, vibratory sense, and proprioception.
- Staggering gait, frequent falling, nystagmus, dysarthria, pes cavus, hammer toes, hypertrophic cardiomyopathy (cause of death).
- Friedreich is Fratastic (frataxin): he’s your favorite frat brother, always stumbling, staggering, and falling, but has a big heart.
15
Q
Brown-Séquard syndrome
A
- Hemisection of spinal cord.
- Findings:
- Ipsilateral UMN signs below the level of the lesion (due to corticospinal tract damage)
- Ipsilateral loss of tactile, vibration, proprioception sense 1–2 levels below the level of the lesion (due to dorsal column damage)
- Contralateral pain and temperature loss below the level of the lesion (due to spinothalamic tract damage)
- Ipsilateral loss of all sensation at the level of the lesion
- Ipsilateral LMN signs (e.g., flaccid paralysis) at the level of the lesion
- If lesion occurs above T1, patient may present with Horner syndrome due to damage of oculosympathetic pathway.
16
Q
Horner syndrome
- Symptoms
- Lesion
- Pathway
A
- Symptoms: sympathectomy of face
- Ptosis (slight drooping of eyelid: superior tarsal muscle)
- Anhidrosis (absence of sweating) and flushing (rubor) of affected side of face
- Miosis (pupil constriction)
- PAM is horny (Horner).
- Ptosis, anhidrosis, and miosis (rhyming).
- Lesion
- Associated with lesion of spinal cord above T1 (e.g., Pancoast tumor, Brown-Séquard syndrome [cord hemisection], late-stage syringomyelia).
- Pathway
- The 3-neuron oculosympathetic pathway projects from the hypothalamus to the intermediolateral column of the spinal cord, then to the superior cervical (sympathetic) ganglion, and finally to the pupil, the smooth muscle of the eyelids, and the sweat glands of the forehead and face.
- Interruption of any of these pathways results in Horner syndrome.
17
Q
Landmark dermatomes
- C2
- C3
- C4
- T4
- T7
- T10
- L1
- S2, S3, S4
- Diaphragm and gallbladder
A
- C2—posterior half of a skull “cap.”
- C3—high turtleneck shirt.
- C4—low-collar shirt.
- T4—at the nipple.
- T4 at the teat pore.
- T7—at the xiphoid process.
- T10—at the umbilicus (important for early appendicitis pain referral).
- T10** at the belly butten.**
- L1—at the inguinal ligament.
- L1 is IL (Inguinal Ligament).
- L4—includes the kneecaps.
- Down on ALL 4’s (L4).
- S2, S3, S4—erection and sensation of penile and anal zones.
- “S2, 3, 4 keep the penis off the floor.”
- Diaphragm and gallbladder pain referred to the right shoulder via the phrenic nerve.
18
Q
Clinical reflexes
- Nerve roots
- Biceps
- Triceps
- Patella
- Achilles
- Reflexes
- S1, 2
- L3, 4
- C5, 6
- C7, 8
- Additional reflexes
- L1, L2
- S3, S4
A
- Nerve roots
- Biceps = C5 nerve root.
- Triceps = C7 nerve root.
- Patella = L4 nerve root.
- Achilles = S1 nerve root.
- Reflexes count up in order
- S1, 2—“buckle my shoe” (Achilles reflex)
- L3, 4—“kick the door” (patellar reflex)
- C5, 6—“pick up sticks” (biceps reflex)
- C7, 8—“lay them straight” (triceps reflex)
- Additional reflexes
- L1, L2—“testicles move” (cremaster reflex)
- S3, S4—“winks galore” (anal wink reflex)
20
Q
Brain stem—ventral view
A
- CNs that lie medially at brain stem: III, VI, XII.
- 3(×2) = 6(×2) = 12
- Motor = Medial
21
Q
Brain stem—dorsal view (cerebellum removed)
- Pineal gland
- Colliculi
- Superior colliculi
- Inferior colliculi
- Parinaud syndrome
A
- Pineal gland
- Melatonin secretion, circadian rhythms.
- Colliculi
- Superior colliculi
- Conjugate vertical gaze center.
- Inferior colliculi
- Auditory.
- Your eyes are above your ears, and the superior colliculus (visual) is above the inferior colliculus (auditory).
- Superior colliculi
-
Parinaud syndrome
- Paralysis of conjugate vertical gaze due to lesion in superior colliculi (e.g., pinealoma).
