Spinal cord lesions Flashcards
ascending tracts
sensory
- dorsal column
- spinothalmic
descending tracts
motor
- corticospinal
where does the spinal cord end and become the cauda equina
L1
cauda equina
collection of peripheral nerves that travel within the spinal cord
Dorsal columns
- The dorsal columns travel in the posterior section of the spinal cord and carry information about fine touch, vibration sense, and proprioception.
- When the cars carrying this information enter the spinal cord, they don’t really bother changing lanes until they are almost at their destination.
- The fibres remain ipsilateral and do not decussate until they reach the medulla of the brainstem.
Spinothalamic tracts
- The spinothalamic tracts travel in the anterior part of the spinal cord and carry information regarding pain and temperature.
- Cars carrying this information cross over into the outside lane almost immediately and stay in this lane until they reach their destination: the fibres decussate as soon as they enter the spinal cord and ascend contralaterally.
decussation in the dorsal columns vs spinothalamic
one significant descending tract
corticospinal tract
The corticospinal tract
- Carries motor information from the motor centres of the frontal lobe down to the skeletal muscles; cars are driving down the motorway, away from the brain, towards other areas.
- Like to the spinothalamic tracts discussed above, when the fibres of the corticospinal tracts get onto the motorway, most immediately change lanes and remain in the opposite lane until they reach their destination: the fibres travel contralaterally.
blood supply to the spinal cord
Anterior spinal artery
- supplies anterior 2/3 (bilateral symptoms)
2 Posterior spinal arteries
- - supplies posterior 1/3 (unilateral symptoms)
blood supply to the spinal cord
Anterior spinal artery
- supplies anterior 2/3 (bilateral symptoms)
2 Posterior spinal arteries
- - supplies posterior 1/3 (unilateral symptoms)
Signs that may indicate that the problem is in the spinal cord rather than other parts of the nervous system.
- Mixed upper and lower motor neurone signs
- Sensory level
- Sphincter involvmeent
- Autonomic dysfunction
- Pattern of clinical signs
Mixed upper and lower motor neuron signs
As the spinal cord is part of the central nervous system, there will be upper motor neuron signs (increased tone, clonus, hyperreflexia, extensor plantars). The spinal nerves leaving the spinal cord at the level of the lesion may also be damaged.
As these nerves are part of the peripheral nervous system there will also be lower motor neuron signs (muscle wasting, fasciculations, flaccid paralysis, reduced reflexes) at the level of the lesion.
Aside from some rare genetic syndromes, the other common diagnosis that may include both upper and lower motor signs is motor neuron disease which is, itself, thought to primarily affect the anterior horn cells of the spinal cord.
Sensory level
There may also be a sensory level, a well-demarcated transverse line below which sensation is abnormal. For example, a lesion at the T10 level of the spinal cord may produce a sensory level around the level of the umbilicus.
Sphincter involvement
Sphincter involvement
Sphincter involvement makes problems in the brain or the brainstem less likely (although not impossible) but both spinal cord and cauda equina lesions can disrupt urinary and bowel function.
- A lesion of the spinal cord results in urinary retention and constipation. The best way to think of this is as increased sphincter tone, preventing the passage of urine or faeces.
- Conversely, a cauda equina lesion would result in urinary and faecal incontinence with flaccid paralysis of the urethral sphincter.
Brown-Sequard syndrome
Cause: damage to one lateral hald of the spinal cord (most commonly cervical)
Pahtophysiology
- different tracts decussate in different locations
- therefore classicial clinical rpesentation of a thorasic spinal cord hemispection is of spastic paralysis and loss of pain and temperature senstation in one leg,
–> due to interruption of the coritcospinal and spinothalamic tracts
- Due to the variable decussation levels, there will also be loss of fine touch, proprioception and vibration sense in the other (dorsal column)
BILATERAL BUT ASYMMETRICAL
anterior cord syndrome
Stroke in the anterior spinala artery
- ASA supplies 2/3s of the spinal cord
- Bilateral SYmptoms
Presentation
- Bilateral disruption of the spinothalamic tract (loss of pain and temprature sensation)
- Bilateral disruption pof of corticospinal tracts (spastic paralysis and UMN signs)
what wont be affected: dorsal columns (posterior position
Posterior cord syndrome
Conversely to anterior cord syndrome, it is also possible to develop a posterior spinal cord syndrome. This causes unilateral damage to the dorsal columns.
The corticospinal tracts can also be affected but the spinothalamic tracts will be spared. This is often the clinical picture seen in subacute combined degeneration of the spinal cord as a result of B12 deficiency.2
Syringomyelia
Also called central cord syndrome , occurs due to the development of a fluid-filled cyst (a syrinx) around the spinal canal.
Syringomyelia is primarily a problem with CSF flow and is commonly associated with the Chiari malformation.4
As the spinal canal is immediately surrounded by decussating fibres making up the spinal white matter, it is these that are initially affected. Despite beginning in the central white matter, it may expand and eventually affect the corticospinal and spinothalamic tracts.
The pattern of deficit seen in patients with syringomyelia initially seems confusing as it is different from other syndromes. The upper limbs are affected first whilst the lower limbs are spared until much later.
As the fibres of the spinothalamic tract enter the spinal cord and immediately decussate, they pass close to the spinal canal, meaning they are often the first of these white matter fibres to be compressed and damaged.
**As the cervical cord is the most likely location of the lesion, there is classically said to be a “cape-like” loss of pain and temperature sensation.
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