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Syringomyelia
This is a cyst or cavity that forms within the spinal cord.
Due to the organisation of the sensory pathways, it affects the decussating fibres of the spinothalamic system affecting pain and temperature sensation, and it does not affect the dorsal column neurones.
Causes
Acquired – post meningitis/arachnoiditis, spinal cord tumour or injury
Congenital – associated with the Chiari malformation (lower cerebellum protrudes through the foramen magnum into the cervical canal) which blocks the flow of CSF
Symptoms
Cape-like” distribution of absent pain and temperature
Spared sense of touch, vibration and proprioception
If it is associated with the Chiari malformation, coughing or Valsalva manoueveres increases CSF pressure causing a transient occipital headache and neck pain
LMN signs in arms (wasting of intrinsic muscles of hands and reduced dexterity)
UMN signs in lower limbs, secondary to the compression of corticospinal tracts
Neuropathic pain and bowel/bladder dysfunction (can lead to incontinence)
Key tests
MRI with contrast of spinal cord
Management
Surgical decompression at foramen magnum to allow CSF flow
Brown-Sequard Syndrome
This is a syndrome caused by a lesion (e.g., trauma, inflammation, or tumour) that transects half the spinal cord, i.e., a lateral hemisection.
This leads to damage to the corticospinal tract leading to muscle weakness.
It also affects the sensory systems in different ways. For pain and temperature sensation, as the fibres have already crossed, it leads to loss on the opposite side.
The dorsal column neurones are yet to cross, and so a lesion affects ipsilateral sense of vibration and proprioception.
Symptoms
Ipsilateral muscle weakness below the level of the lesion.
Ipsilateral loss of proprioception and vibration, but contralateral loss of pain and temperature
Degenerative cervical myelopathy (DCM)
This refers to compression of the spinal cord in the cervical region, which can be secondary to column degeneration in osteoarthritis, or a prolapsed disc.
Compression gives progressive symptoms; UMN signs below the level of the lesion and LMN symptoms at the level of the lesion.
Individual nerve roots can also be compressed (radiculopathy) which causes pain, paraesthesia and a LMN pattern of weakness in the muscles innervated by the root.
Symptoms
Back pain and stiffness, often associated with a headache
Reduced manual dexterity and paraesthesia and leg weakness
Urinary/faecal incontinence as a late consequence
Hoffman sign – flicking the distal phalanx of the middle finger gives reflex flexion of the ipsilateral thumb and index finger
Gait ataxia
Key tests
MRI of spinal cord
Management
Neurosurgery for decompression is usually required
Friedreich Ataxia
This is a degenerative condition of the cerebellum and spinal cord.
It leads to the development of ataxia at an early age (around puberty).
It is due to an autosomal recessive expansion of trinucleotide repeat GAA in frataxin which leads to iron build up.
This leads to free radical formation which causes degeneration of many nerve tracts.
Symptoms
Cerebellar degeneration – gait ataxia, nystagmus, dysdiadochokinesis
Presence of both UMN and LMN symptoms – muscle weakness in lower limbs, absent knee and ankle jerks, increased muscle tone (spasticity), dysarthria
Spinal degeneration – kyphoscoliosis
Associated with hypertrophic cardiomyopathy and diabetes mellitus
Key tests
EMG and nerve conduction studies
Genetic testing to confirm diagnosis
Management
No cure available. Manage complications such as diabetes and cardiomyopathy
