Neurology- Motor System

Question 1

Anatomy

Answer 1

-The principle motor pathway has CNS and PNS components
-Other parts of the nervous system, such as the basal ganglia and cerebellum, have important modulating effect on movement
-it is important to distinguish upper from lower motor neuron signs to help localise the lesion

Question 2

Upper motor neuron lesions

Answer 2

• If the lesson affects the CNS pathways, the lower motor neurons are under the uninhibited influence of the spinal reflex
• The motor units then have an exaggerated response to stretch with increased time (spasticity), clonus and brisk reflex
• Primitive reflexes, such as the plantar extensor reflex (Babinski sign), may be present

Question 3

Lower motor neuron lesions

Answer 3

• Motor fibres, together with input from other systems involved in the control of movement, including extrapyramidal, cerebellar, vestibular and proprioceptive efferent
• A lower motor neuron lesion causes weakness and wasting in the muscle fibre, reduces tone (flaccidity), fasciculation and reduced or absent reflexes

Question 4

Basal ganglia lesions

Answer 4

• Basal ganglia are connected structures within the cerebral hemispheres and brainstem
• The striatum, globus pallidus, thalamus, STN and substantia nigra
• Basal ganglia regulates movement control, behaviour and executive function control
• Conditions of the basal ganglia cause reduced movement (PD), sometimes excessive moments (Ballism)

Question 5

How to assess the motor system

Answer 5

• Assessing stance and gait
• Inspecting and palpating muscle
• Assessing tone
• Testing movement and power
• Examining reflexes
• Testing co-ordination

Question 6

Stance and gait

Answer 6

• Stance and gait depends on intact visual, vestibular, sensory, corticospinal, extrapyramidal and cerebellar pathways, together with functioning lower motor neurons and spinal reflexes
• Certain abnormal gait patterns are recognisable, suggesting diagnoses

Question 7

How to examine stance

Answer 7

• Ask the patient to stand with their (preferably bare) feet together and eyes open
• Swaying, lurching or an inability to stand with the feet together and eyes open suggests cerebellar ataxia
• Ask the patient to close their eyes (Romberg’s test) but be prepared to catch them, repeated falling is a positive
• The pull test assess postural stability. Feet slightly apart. Inform them that you are going to pull them backwards.

Question 8

How to examine gait

Answer 8

• Get them to walk assess NB: stride length, arm swing, steadiness and limping
• Look for abnormal movements e.g. tremor or dystonic movements
• Listen for slapping of foot drop
• ask to walk heel-toe in a straight line. This emphasis gait ataxia and may be the only abnormal finding in midline cerebellar (vermis) lesions.
• unsteadiness with eyes open is common in cerebellar disorders
• Romberg’s sign indicates proprioceptive sensory loss (sensory ataxia) or bilateral vestibular failure
• Cerebellar ataxia is not normally associated with Romberg test
• bilateral upper motor neuron damage causes scissor like gait due to spasticity.
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Question 9

Gait in PD

Answer 9

• In PD heel-toe walking may be impossible, the steps are short and shuffling with no arm swing
• Tremor may become more apparent.
• The stopped posture and impairment of postural reflexes can result in a festinant gait
• Postural instability on the pull test occurs in PD

Question 10

Muscle bulk

Answer 10

• Lower motor neuron lesion may cause muscle wasting
• Make disorders usually result in proximal wasting

Question 11

Faciculation

Answer 11

• Fasciculation are visible irregular twitches of resting muscles caused by individual motor units firing spontaneously
• fasciculation is seen not felt
• physiological fasciculation is common

Question 12

Myoclonus jerks

Answer 12

• These are sudden, shock-like contractions of one or more muscles that may be focal or diffuse.
• Healthy people commonly experience these when falling asleep (hypnic jerks)
• They may also occur pathologically in association with epilepsy, diffuse brain damage and some neurodegenerative disorder such as prion disease.
• Negative myoclonus (asterixis) is seen most commonly in liver disease (liver flap)

Question 13

Tremor

Answer 13

• Tremor is an involuntary, oscillatory movements resulting from contraction and relaxation of muscles.
• Tremors are classified according to their frequency, amplitude, position and body part affected
• Physiological tremor is a fine, fast postural tremor
• A similar tremor occurs in hypothyroidism, EtOH excess and B2-agonist bronchodilator
• Essential tremor is the most common. It is typically symmetrical in the upper limbs and may include head and voice
• intention tremor is absent at rest but maximal on movement and on approaching the target and is usually due to cerebellar damage (finger to nose test)
• Other causes include acquired demyelinating neuropathies (e.g. charcot-Marie-tooth disease)

Question 14

Parkinson’s disease tremor

Answer 14

• PD causes a slow coarse, pill-rolling tremor, worse at rest but reduced with voluntary movements
• It is more common in the upper limbs, is usually asymmetrical and does not affect the head, although it may involve the jaw/chin and sometimes in the legs

Question 15

Other involuntary movements

Answer 15

• Dystonia is caused by substantial muscle contractions, leading to twisting, repetitive movements and sometimes tremor
• Chorea describes brief, jerky, random, purposeless movement disorders
• Ballism refers to violent flinging movements sometimes affecting only one side