Spinal Cord Flashcards
Describe the spinal cord
part of the Central Nervous System (CNS)
Organised segmentally - cervical (8), thoracic (12), lumbar (5), sacral (5) and coccygeal (1) which provides 31 segments.
From each segment arise a pair of spinal nerves - left and right - thus 31 pairs of spinal nerves
Where are the spinal nerves in relation to the vertebrae?
Upper 7 cervical nerves pass through the intervertebral foramen above the appropriate vertebra.
Other spinal nerves pass through the intervertebral foramen below the appropriate vertebra. This results in there being 8 cervical spinal segments and nerves while there are 7 cervical vertebrae.
Where does the spinal cord start?
Upper limit of the cord fixed by its attachment to the medulla oblongata
How long are the spinal rootlets?
Vertebral level of lower limit of the cord - L3/L4 in the new-born infant, L1/L2 in the adult. Therefore the spinal rootlets of the cervical nerves are short. But the rootlets of the sacral (and coccygeal) nerves are very long
Describe the craniocervical region
Thick envelope formed by the dura and arachnoid
Rootlets of the spinal nerves - here these are relatively short in length
Dorsal root ganglia in close relation to the intervertebral foramina
Continuous with dura of cranial cavity
What is the conus medullaris?
The conus medullaris - the lower limit of nervous tissue
What is the filum terminale?
The filum terminale - a cord of connective tissue linking the conus medullaris and the 1st coccygeal vertebra
Where does the spinal cord end?
The long rootlets of spinal nerves form the cauda equina
Lower end of the lumbar cistern at S2 where the dura mater narrows to envelop the lower part of the filum terminale
Describe a cross-section of the spinal cord
-Ventral anterior component = Large anterior horn cells -Dorsal posterior component -Afferent neurones Lateral horns in thoracic= sympathetic
What are the lesions of the spinal cord?
Syringomyelia (central fluid filled cavity develops that damage spinothalamic fibres as they decussate)
Trauma
Neoplasm
Thromboembolic disease
Describe Upper cervical spinal cord lesion presentation
Spastic tetraplegia Hyperreflexia Plantar responses extensive Incontinence and sensory loss below lesion Associated proprioceptive problems
Describe lower cervical spinal cord lesion presentation
Upper limbs
Sensation up to level of lesion
What is Hemisection of the cord (Brown-Sequard)?
- Ipsilateral loss of proprioception
- UMN signs
- Contralateral loss of pain and temperature sensation
What do we test in clinical examination?
-UMN/ LMN lesions
-Reflexes
-Spastic/ flaccid paralysis
Patellar tendon reflex
What do we move to test strength?
Shoulder Elbow Wrist Knee Hip Ankle What level of spinal cord movements
Spinal cord pathology
Traumatic
Vascular- vascular myelopathy
Infection/ inflammation- myelitis
Neurodegeneration- motor neurone disease/ spinal muscular atrophy
Describe Anterior spinal artery thrombosis
Common disorder Supplies two thirds of spinal cord LMN signs that progress to UMN Loss of sensation and autonomic function Preservation of proprioception through posterior columns
Peripheral nerve lesions
Brachial plexus
-Traction lesions
=Upper roots (C5+C6)- Erb’s palsy; “waiter’s tip” position of the arm
=Lower roots (C8+T1)- “claw hand” deformity
-Neoplastic involvement
-Post-irradiation
Describe radial nerve damage
Damaged by fractures to the mid-shaft of humerus
C6-C8
Compression at same site leading to “Saturday night paralysis”
loss of extension of wrist and fingers (wrist drop)
Sensory problems in dorsal aspect of hand
Describe median nerve damage
Carpal tunnel syndrome; predominantly sensory but maybe associated with wasting of thenar muscles.
C5-T1, predominantly C6
Sensory loss in palm
Describe ulnar nerve damage
May be damaged by injury at the medial epicondyle of the elbow, or at the medial aspect of the wrist.
C7,8,T1
Characteristic “claw hand” deformity.
Describe Femoral nerve damage
May be damaged by hip dislocation, pelvic fracture, and tumours in the pelvis.
L2-L4 lumbosacral plexus
Leads to weakness of knee extension (results in inability to lock knee while walking) and some wasting of quadriceps.
Describe Sciatic nerve damage
This is composed of two large trunks which are bound together and separate in mid-thigh
tibial nerve
peroneal nerve
Damage to the sciatic nerve can be due to trauma, neoplastic compression/infiltration, or operative complication.
Results in foot drop and unstable ankle
L4-S3
What is Sciatica?
Much more common is compression or irritation of a spinal root which comprises the sciatic nerve (sciatica)
Symptoms dependant on the nerve root
-Common
L5; sensory- pain in posterolateral thigh and leg, numb inner foot
motor- weakness of dorsiflexing foot and toes
S1; sensory- pain in posterolateral thigh and leg, numb lateral foot
motor- weakness of foot dorsiflexion and loss of ankle jerk
-Rare
L3+L4- diminished knee jerk, pain in anterior thigh
What is a prolapsed intervertebral disc?
Annulus fibrosis- deteriorate posteriorly
Fluid nucleus pulposus= prolapse
Pressure onto spinal nerve root behind
How is a prolapsed disc resolved?
Resolve spontaneously
Operate= Microdiscectomy= access posteriorly, remove prolapsed material
Describe damage to the common peroneal nerve
This can be damaged as it winds round the head of the fibula. This can be by fracture or compression (e.g. tight cast).
Results in weakness of foot dorsiflexion and eversion.
L4-S2
