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Neuro > Neurolocalisation > Flashcards

Neurolocalisation Flashcards

1
Q

What is neurolocalisation?

A

Using the pattern of a lesion to determine its site.

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2
Q

What is the motor axis?

A
  • Pathway for motor signals (cortex > cerebellum and basal ganglia > descending spinal tracts > muscles)
  • Cortex initiates movement
  • Basal ganglia determines quantity of power
  • Cerebellum determines coordination
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3
Q

What is the normal reflex arc?

A
  1. Afferent sensory neuron synapses into two neurons in the spinal cord - the ascending tract neuron, and the efferent LMN
  2. Ascending tract neuron communicates info to the cortex; cortex sends signals back down via descending pathways (UMN) to initiate, quantify, and coordinate movement
  3. Simultaneously, the LMN is also sending out its own immediate reflex actions, which are then modulated by the incoming UMN signals
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4
Q

How does a UMN lesion work?

A
  • In a UMN lesion, there is no longer any modulation of descending motor signals.
  • Reflex arc is uninhibited
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5
Q

How does an LMN lesion work?

A
  • In an LMN lesion, there is no longer any transmission of motor signals from the spinal cord to the muscles
  • Reflex arc is broken
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6
Q

What are the UMN lesion signs?

A
  1. Weakness / Paralysis
  2. Spasticity (hypertonia, hyperreflexia)
  3. Clonus (involuntary muscle contractions)
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7
Q

What are the LMN lesion signs?

A
  1. Weakness
  2. Hypotonia, absent reflexes
  3. Denervative changes (muscle wasting from disuse, fasciculations from hyperexcitability and spontaneous electrical activity)
  4. Postural instability
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8
Q

What is a general difference between the patterns of lesion for the brain VS for the spinal cord?

A
  • Brain: unilateral, contralateral / ipsilateral
  • SC: bilateral, sphincteric signs, LMN signs at lesion level + UMN signs below lesion level
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9
Q

For the brain and its cranial nerves, which components are considered to be the UMNs / LMNs?

A
  • UMNs: cerebral cortex, brainstem
  • LMNs: cranial nerves
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10
Q

What is the difference between LMN and NMJ lesions?

A
  • NMJ lesion only leads to partial weakness, as not all NMJs in the muscle may be affected
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11
Q

Name the different lobes of the cortex, and what effects a lesion in those sites would have on the body.

A
  1. Frontal lobe - hemiparesis / hemiplegia
  2. Parietal lobe - sensory deficits
  3. Temporal lobe - cognitive deficits (dysgraphia, dysphasia, dyscalculia, agnosia (lack of recognition), hemispatial neglect (unable to perceive things on one side)
  4. Occipital lobe - visual defects
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12
Q

What effects would a cerebellar lesion have?

A

Ipsilateral ataxia

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13
Q

What is the pattern for brainstem lesions?

A
  • Contralateral effects on the body
  • Ipsilateral effects on the face
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14
Q

What is locked-in syndrome?

A

Severe spinal tract lesion causes severe sensorimotor deficits - patient is aware, but cannot move or communicate as their muscles are almost all paralysed (except vertical eye movements and blinking)

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15
Q

What effects would a lesion in the tracts to / from the cerebellum have?

A
  • Ataxia
  • Vertigo
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16
Q

What effects would a lesion in the reticular formation of the brainstem have?

A
  • Impaired consciousness
  • Impaired breathing (Cheyne-Stokes breathing)
17
Q

Outline the pathophysiology of Cheyne-Stokes breathing.

A
  • Cyclic abnormal breathing pattern, due to delayed feedback between chemoreceptors and respiratory centers in the RF
  1. Gradual hyperpnea: initial high CO2 levels (accumulated from delayed breathing response) slowly stimulate delayed compensatory respiration
  2. Gradual hypopnea: as CO2 levels drop, respiration decreases in a delayed fashion
  3. Apnea: CO2 levels drop below threshold for respiration due to delayed decrease in respiration, leading to accumulation in CO2
18
Q

What effects would a lesion in the autonomic regions of the brains have?

A

Horner syndrome - disruption of sympathetic innervation to one side of the face (ptosis, miosis, anhidrosis)

19
Q

What are the general functions of the major spinal tracts?

A
  1. DCML (fine sensations): fine touch, vibration, two-point discrimination, conscious proprioception
  2. Spinocerebellar: unconscious proprioception
  3. Spinothalamic (crude sensations): crude touch, pain, temperature, pressure
  4. Corticospinal (motor): voluntary, skilled movements of the body
20
Q

Where do the spinal tracts decussate, if any?

A
  1. DCML - medulla oblongata
  2. Spinocerebellar - NO
  3. Spinothalamic - spinal cord
  4. Corticospinal (Lat.) - medulla oblongata
  5. Corticospinal (Ant.) - spinal cord
21
Q

What tracts are affected, and what is the resulting effect, in anterior cord syndrome?

A
  1. Spinothalamic = loss of crude sensations
  2. Corticospinal = LMN signs at lesion level, UMN signs below
  3. SC lesion = sphincteric involvement
22
Q

What tracts are affected, and what is the resulting effect, in posterior cord syndrome?

A
  1. DCML = loss of fine sensations
  2. Corticospinal = LMN signs at lesion level, UMN signs below
  3. SC lesion = sphincteric involvement
23
Q

What tracts are affected, and what is the resulting effect, in hemisection of spinal cord?

A
  1. DCML - ipsilateral loss of fine sensations
  2. Spinocerebellar - ipsilateral loss of unconscious proprioception
  3. Spinothalamic - contralateral loss of crude sensations
  4. Corticospinal - LMN signs at lesion level, UMN signs below
  5. SC lesion = sphincteric involvement
24
Q

What pattern of signs would be observed in a peripheral nerve lesion?

A

LMN signs

25
Q

What are two brachial plexus palsies?

A
  1. Erb’s Palsy - superior brachial plexus injury
  2. Klumpke’s Palsy - inferior brachial plexus injury
26
Q

Describe Erb’s Palsy.

A
  • C5 and C6 injured
  • Shoulder abduction (deltoids) + elbow flexion (biceps, brachialis) + wrist extension (brachioradialis) affected
  • waiter’s tip (adducted shoulder, extended elbow, flexed wrist)
27
Q

Describe Klumpke’s Palsy.

A
  • C8 and T1 injured
  • Finger / thumb abduction (short muscles of the hand) affected
  • claw hand
28
Q

Describe lumbosacral plexus injury.

A
  • L4 to S1 injured
  • Hip movements, knee movements, thigh adduction, and ankle / foot movements affected
  • Loss of sensation over leg
  • Deep, aching pain that radiates from lower back into leg
29
Q
A

Neuro (18 decks)

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