3.1.3 Somatosensory Conditions Flashcards
What is brown sequard syndrome?
Complete cord hemisection causing destruction of one lateral half of a single cord segment resulting from trauma or ischaemia
What structures are completely destroyed unilaterally in brown sequard syndrome?
Dorsal horn
Ventral horn
All other cord grey matter
All white matter pathways
Dorsal and ventral roots
What signs are present in brown-sequard syndrome?
Ipsilateral complete segmental anaesthesia affecting a single dermatome (due to destruction of doral root and horn)
Ipsilateral loss of dorsal column modalities below destroyed segment as the dorsal columns cannot ascend, they ascend on the same side until the level of the medulla, e.g. L2 lesion, everything from L2 and below would not be able to ascend
Contralateral loss of spinothalamic modalities at and below the destroyed segment
There is contralateral loss as ST second order neurones decussate at the level of primary neurones and try to ascend on the affected side, but ipsilateral axons cross and ascend on the unaffected side
What does Lissaeur’s tract allow in lesions?
Allows preservation of function up to a couple of segments lower
Allows primary sensory neurones to ascend higher than their segmental level, e.g. C5 can ascend up to C3 and C6 can ascend to C4. So if a C5 lesion may have function up to C7
What do A and C fibres do?
A fibres- carry impulses from mechanoreceptors in skin
C fibres- carry pain
What do inhibitory interneurones contain
Contain the endorphin encephalin which can be stimulated to inhibit pain conduction
How can pain receptors be inhibited in spinal cord?
Second order neurones dealing with pain receive nociceptive primary afferents and inhibitory interuones
Encephalinergic interneurones can be activated by impulses from mechanoreceptors
e.g. rubbing a sore area causes mechanoreceptor stimulation, this activates inhibitory encephalinergic interneurones, release of encephalin inhibits pain
How else can encephalinergic interneurones be activated?
From descending inputs from higher centres such as the periaqueductal grey matter or the nucleus raphe magnus
If a patient has a tumour compressing the left cerebral peduncle, what effect will there be on the sensory system?
No sensory effects, cerebral peduncles contains motor fibres only
Sensory fibres ascend directly to the thalamus
If a patient has a dorsal column lesion, what will happen if they stand up and close their eyes?
Dorsal column lesion leads to loss of proprioception, vibration, light touch and 2 point touch
If this patient stands up and closes their eyes, they will have no proprioception and vision, therefore they will lose their balance
A patient has lost all sensory modalities in the left T3 dermatome, loss of pain temperature and sensation from T4 downwards on the right side and loss of vibration and light touch from T4 downwards on the left side, where is the lesion?
T3 both spinothalamic and dorsal column affected
Pain and temperature are spinothalamic modalities, T4 downwards on right side
Vibration and light touch are dorsal column modalities, so…
Left T3 both DC and ST
Right T4 ST
Left T4 DC
DC is ascending on the affected side and ST decussates so the lesion must be a left sided T3 as there is no loss of left sided ST, the left sided DC is trying to ascend through the lesion and the right sided ST has decussated and is trying to ascend through the lesion
Left side of T3 cord segment
A patient has bilateral loss of temperature and pain in C6,7 and 8, why?
Temperature and pain are spinothalamic modalities
Bilateral loss suggests its either a midline or systemic cause
Tumours affected both thalami would be extremely rare, cord damage would affect segments below the lesion
Syringomyelia affected C6-8
Syringomyelia= fluid-filled cyst which forms in the spinal cord
A patient has loss of all sensory modalities confined to the medial surface of the upper limb including the medial surface of the hand, where is the lesion likely to be?
Remember from dermatome map, medial upper limb is T1,2,3 etc..
Medial surface of hand is C8
So if C8,T1,2,3 etc are affected the lesion must start at C8
