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.