Spine Flashcards
Questions covering required knowledge of spinal anatomy for the primary FRCA exams, particularly relevant for the SOE and OSCE. There is considerable overlap with neurophysiology in past spinal anatomy stations for the OSCE, and this is reflected in these flashcards.
For a lumbar epidural block, what volume of local anaesthetic is required per segment to be blocked?
1.5 - 2.0 ml
What is the total cerebrospinal fluid (CSF) volume in the adult?
100 - 200 ml
What is the normal spinal CSF pressure in the supine patient?
7 - 20 cm H2O (5-15 mm Hg)
In a transverse section of the spinal cord, of what is the grey matter composed?
Nerve cell bodies and unmyelinated axons
What does the dorsal root ganglion contain?
Cell bodies of the afferent neurons
Describe the neurological pathway followed after stimulation of a nociceptor by a painful stimulus from the point of entry into the spinal cord
Enters the spinal cord via the posterior nerve root, synapses in the dorsal horn, crosses the midline to ascend in the lateral spinothalamic tract. After synapsing in the thalamus, impulses are relayed to the sensory cortex
Identify the lateral spinothalamic tract on the diagram
Area marked A
What modality is carried by the anterior spinothalamic tract?
Touch (coarse touch & pressure)
Which spinal tracts are represented by the area marked B?
Spino-cerebellar tracts (anterior and posterior).
These tracts are responsible for proprioceptive signals, obtained from the golgi tendons and muscle spindles.
What does the area marked C on the diagram represent and what modalities are carried by it?
Dorsal/posterior columns.
Proprioception from skin and joints, fine touch, vibration, two-point discrimination
What is the specific gravity of CSF?
1003-1009 (1.003-1.009)
Which spinal tracts are represented by area E
Anterior corticospinal tracts (innervate axial muscles)
Which spinal tract is represented by Area D?
Lateral corticospinal tract (limb muscles)
What type of nerve impulses travel in the corticospinal tracts and how do the fibres terminate?
Descending motor impulses.
They synapse with motor neurones in the anterior horn.
Within the spinal cord, where are ascending pain and temperature fibres carried?
Lateral spinothalamic tract
What vessels contribute to the arterial blood supply of the cord?
Anterior spinal artery
Posterior spinal artery (arises from vertebrals or PICA)
Spinal branches of the vertebral, intercostal, lumbar and sacral arteries
*Great anterior medullary artery (Artery of Adamkiewicz) - this usually arises on the left from a posterior intercostal artery between level T9-12
What are the different ways to describe/classify an acute spinal cord injury?
Level of injury
- cervical and thoracic injuries most common
Stability of vertical columns
- anterior column - anterior longitudinal ligament → first 2/3rds of veterbrae and intervertebral discs
- middle column - last 1/3 of the verterbrae and IV discs → posterior longitudinal ligament
- posterior column - PLL → supraspinal ligament
Extent of injury
- 50% will be complete transections
Describe the course of the major descending tract (CST)
Upper motor neurons leaves the motor cortex (located in the precentral gyrus) and track along the posterior limbs of the internal capsules to the medullary pyramids.
90% of the fibres decussate in the medullary pyramids and descend in the lateral corticospinal tracts (to innervate limb muscles), and 10% descend in the ipsilateral anterior corticospinal tracts (to innervate truncal axial muscles) where the fibres cross at the level they innervate.
The upper motor neurons synapse in the anterior/ventral horns with the lower motor neurons which exit via the ventral roots and merge with the dorsal roots as part of the spinal nerves, terminating at the motor end plates of the muscles they innervate.
What are the deficits in Brown-Sequard syndrome?
Ipsilateral paralysis below level of lesion
Ipsilateral loss of fine touch, vibration and position sense below the level of the lesion
Contralteral loss of pain and temperature sensation 1 or 2 levels below lesion
Describe the primary course of pain and temperature sensation from stimulus to cortex.
(Spinothalamic tract)
Pain and temperature stimuli are received by nociceptors and thermoreceptors in the skin, joints or viscera inducing action potentials in primary order neurons.
The axons of the primary order nerves enter the spinal cord via the dorsal nerve roots (their cell bodies lie in the dorsal root ganglia) and ascend or descend one or two levels in Lissauer’s tract before synapsing with second order neurons in the dorsal horn.
The axons of the second order neuron cross the spinal cord at this level in the anterior commisure, before ascending in the contralateral spinothalamic tract to the thalamus, where they synapse with third order neurons which convey the impulse to the post-central gyrus, which forms the sensory cortex.
Describe the primary course of fine touch (two-point discrimination), vibration and position sense (proprioception) from stimulus to cortex.
(The dorsal column-medial lemniscus pathway (DCML))
The first order neuron enters the dorsal root and ascends in the dorsal column.
Specifically neurons from the lower body (below T6-8) ascend the cord in the more medial fasciculus gracilis and neurons from the upper trunk and limbs (above T6-8) ascend in the more lateral fasciculus cuneatus.
In the medulla the neurons of each fascicle synapse with second order neurons in the gracile and cuneate nuclei, which together are known as the dorsal column nuclei.
Second order neurons, ascending as the internal arcuate fibres, decussate above the nuclei and continue their ascent as the medial lemniscus to the thalamus, where they synapse with 3rd order neurons destined to terminate in the post-central gyrus (sensory motor cortex).
