Ch3 Neurophysiology Flashcards
(53 cards)
What structures form the BBB?
Endothelial tight junctions (within the capillaries)
What is the effect of steroids on BBB?
Reduce the penetration of small hydrophilic molecules
Which areas are the BBB deficient? (6 areas)
Choroid plexus Posterior pituitary Tuber cinereum Area postrema Pineal gland Pre-optic recess
What are the 3 types of oedema?
Cytotoxic (no enhancement) e.g. TBI Vasogenic (enhancement) e.g. tumour Ischaemic (delayed enhancement) e.g. stroke
What is the triple flexor response?
Seen in UMN lesion in addition to babinski reflex, the knee and hip also flex.
What is the anatomy of the Babinski reflex?
S1 dermatome stimulation > tibial nerve > spinal cord L4 to S2 > common peroneal nerve > toe extension
What other tests can be used in addition to Babinski?
Schaeffer = pinch achilles; Gordon = pinch calf; Oppenheim = slide knuckles down shin Stronsky = pull 5th toe and allow it to snap back
What does a Hoffmann’s reflex represent?
Disinhibition of a C8 reflex i.e. lesion above C8
What proportion of patients with cervical myelopathy have a positive Hoffmann’s?
2/3
Where is the primary centre for bladder function?
Locus coeruleus of the pons
What is the function of the locus coeruleus?
Synchronises bladder contraction with urethral relaxation
How is voluntary cortical micturation controlled?
Mesial frontal lobes and genu of CC > pontine locus coeruleus > detrusor contraction and relaxation of the internal urethral sphincter under parasympathetic control. The external sphincter sympathetic tone relaxes through the pudendal nerve.
When is the Babinski reflex negative in SCI?
During spinal shock
Where do the bladder efferents run in the spinal cord?
Lateral to the dorsal columns
Where are the parasympathetic preganglionic cell bodies?
S2-4. The fibres then run via the pelvic splanchnics nerves
Where are sympathetic cell bodies located?
T1-L2
Which tract do bladder sensory fibres run in?
Spinothalamic tract
What is a neurogenic bladder / areflexia?
Lack of sensory input from the bladder wall leads to stretching and overflow incontinence without feeling
What is detrusor hyperreflexia
Efferent lesions from cortex to sacrum cause loss of cortical inhibition and reflex contraction of the bladder
How does a cortical lesion affect bladder function?
Loss of inhibition of the pontine voiding reflex. Results in involuntary reflex bladder contraction and voiding as sensation is intact. Treat with anticholinergics
How does a complete spinal cord lesion affect bladder function?
Initially - spinal shock causes an areflexic bladder and retention. After this the bladder becomes hyperreflexic. Treat with intermittent catheterisation and anticholinergics
When are bulbocavernosus and anal wink reflexes lost?
With cauda equina lesion
How can the bladder function be evaluated?
Urodynamic testing, sphincter EMG and micturating cystourethrogram.
How is detrusor hyperreflexia treated?
antimuscarinics e.g. oxybutynin, these relax the bladder wall and increase capacity so should be combined with a timed voiding regime.
