Motor neurone diseases

Question 1

What occurs in lower motor neurone lesions?

Answer 1

• patient has lost all motor power in the muscles which extend (lift up) the wrist and fingers- a lower motor neurone lesion has occured following a divided radial nerve in the arm
• The patient has these symptoms becaus eno impulses are getting through the affected muscles at all - loss of different innervation

Question 2

What is locked-in syndrome?

Answer 2

• Damage to basallar pons
• Significant loss of function associated with corticobulbar and corticospinal tracts
• Paralysis of most motor functions including limbs and functions associated with motor cranial nerves
• Only blink and vertical gaze retained

Question 3

How do we test for pyramidal tract neurone activity before the contraction of muscle?

Answer 3

• Using a monkey-lever task
• PTN activity starts before movement
• Lever movement

Question 4

What is the brain-machine interface?

Answer 4

• Implanted on MI motor cortex
• acquires brain signals, analyzes them, and translates them into commands that are relayed to an output device to carry out a desired action.

Question 5

What is the role of motor cortex?

Answer 5

Positive sensory feedback
1) Primary somatosensory cortex delivers proprioceptive and tactile inputs to
motor cortex. Ml neurones therefore also discharge in response to movement

2) Supplementary motor area (SMA) receives inputs from basal ganglia and
cerebellum. Has an important role in coordinating voluntary movement.
Patients with SMA lesions display apraxia —
inability to initiate specific, purposeful
movements

3) Premotor cortex (PM) plays a role in movements taht require visual guidance

4) Posterior parietal cortex plays a role in movements that require visual guidance
e.g. paying attention to spatial arrangements of objects in the visual field.
Integrates somatosensory and visual inputs to area 6
Patients with PPC lesions display apraxia & sensory neglect (anosagnosia)

5) Cerebellum and basal ganglia
Thalamus
Basal Ganglia
Motor cortex

Purposeful movement is preceded by discharge of neurones in the cerebellum
and basal ganglia, which occurs prior to discharge of neurones in motor cortex
Thus basal ganglia and cerebellum provide the motor cortex with a planning mechanism for the initiation and regulation of given response

Question 6

What is a cerebral stroke (motor cortex)?

Answer 6

• Largest branch of internal carotid supply includes primary motor and sensory areas of lateral cerebral cortex
• MRI scan showing infarction following occlusion of middle cerebral artery
• Problems with fine movement of extremities

Question 7

What is the motor cortex?

Answer 7

• a circumscribed region of the frontal lobe (Brodmann;s areas 4& 6)
• The motor cortex is somatotopically organised and contains the upper motor neurone cell bodies
• Issues motor commands to the contralateral musculature ( left motor cortex controls right body)