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290 Chapter 7: Nervous system

It should be differentiated from general symptoms of Patterns of neurological disorders

weakness such as fatigue. See Fig 7.2.
Muscle weakness due to lack of use develops rapidly,

forexampleinthelegsduetoapainfulhiporfollowing
Upper motor neurone signs
surgery or a debilitating illness.
Distributionoftheweakness,onsetandanyassociated The motor pathway originates in the precentral gyrus,

pain, e.g. back pain may point to a cause. with corticospinal tracts which pass down through the
Although formal assessment of muscle weakness takes internal capsule, then into the brainstem, where they
place in the examination, certain questions to assess the cross over (the pyramidal decussation) and then pass
functional ability of the patient are required: down to the contralateral spinal cord. Any lesion along
Can you carry and lift objects as you could before? this pathway can lead to upper motor neurone signs

(assesses hand and upper limb power). (UMN). Depending on the level of the lesion the weak-
Can you get up from a chair easily? Do you need nessmaybeipsilateralorcontralateraltothelesion.Signs

to use your arms to help you get up from a include:
chair or to climb up stairs? (assesses lower limb Pronator drift (downward drift and inward rotation
power). of the upper limb with pronation).

Mononeuropathy, e.g. ulnar Dermatomal loss occurs in
nerve lesions. Usually associated dorsal root. All modalities
with motor lesions. of sensation are lost.

Glove and stocking sensory loss in all modalities (pain, temperature,
vibration and joint position sense) occurs in peripheral neuropathies.
These affect the longest nerves first, hence the distribution. They may
have peripheral muscle weakness, which is also bilateral, symmetrical
and distal.

Bilateral symmetrical loss of all modalities of sensation occurs with a
transverse section of the cord. These lesions are characteristically
associated with lower motor neurone signs at the level of transection
and upper motor neurone signs below the level. Cervical lesions lead
to a quadriplegia, thoracic lesions to paraplegia.

Hemisection of the cord causes an ipsilateral loss of vibration and
proprioception and contralateral loss of pain and temperature termed
'Brown–Séquard Syndrome'. There are also ipsilateral upper motor
neurone signs below the level of the lesion and lower motor neurone
signs at the level of the lesion. This arises due to the level at which
the different pathways decussate.

Figure 7.2 Patterns of sensory loss.