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Syringomyelia

Definition

  • Condition in which tubular cavities containing fluid are present within the spinal cord Syrinx = Tube or pipe
  • Classically progressive & producing
  • Dissociative anaesthesia Loss of pain & temperature Intact fine touch, proprioception, vibration Muscle wasting Typically more UL than LL Scoliosis Neuropathic arthropathy

Epidemiology

  • Males > Females No familial tendency

Classification

  • Williams (1970) 1. Communicating Cysts communicate with CSF pathways Chiari 1 malformation (? communicating A-C malformation) Chiari 2 malformation (? noncommunicating A-C malformation associated with SB) Basilar arachnoiditis 2. Non-Communicating No communication with CSF pathways Post-traumatic syringomyelia Neoplastic syrinxes Syrinxes associated with neoplastic arachnoiditis
  • Communicating form generally communicates through obex at caudal portion of the 4th ventricle
  • With time & caudal passage of the brain stem the communication with the 4th ventricle is obliterated & converted to non-communicating

Aetiology

  • Idiopathic Hindbrain herniation Arnold-Chiari malformation Arachnoiditis Post-traumatic Extrinsic compression Causing central cord necrosis Intramedullary tumour Necrotic myelitis

Pathogenesis

All related to disassociation of pressures between the intraspinal & intracranial compartments

Arnold-Chiari Malformation/ Basal arachnoiditis

Restriction of CSF movement through the foramen magnum & prolonged time to equilibriate between the intracranial & intraspinal compartment Thus with valsalva manoeuvre ↑ in the syrinx & developing size of cavity

Post-Traumatic

Unsure mechanism after cord trauma Maybe secondary to block from arachnoiditis Occurs in 2-3% after cord trauma More common in complete tetraplegics Occurs 3 months to 3 years after injury

Neoplasm

Proteinaceous fluid around the tumour This dissects into the cord & enlarging cavity follows

Sudden ↑ in pressure in the syrinx from epidural vein engorgement leads to enlargement & acute deterioration in function (can occur with sneeze & cough)

Cord damage following the syrinx is predictable

Initially see the decussation of the anterior fibres of the spinothalamic tracts involved » Dissociative anaesthesia Loss of pain & temperature Normal light touch Then as enlarges the corticospinal tracts become involved » Motor symptoms follow As the lesion occupies the whole canal then » Legs become spastic & arms weak » Involvement of light touch also Involvement of second order neurons occurs » Causalgic pain

Consequences

Dissociative sensory loss Spastic paraparesis LL/ Weakness in UL Loss of superficial abdominal reflexes Neuropathic joints ~ Especially GHJ Scoliosis

Pathology

Gross Most common level is lower cervical May extend up into the medulla or down into the lumbar cord Fluid filled cavity that is usually separate from central canal but can communicate

Histology

Cystic space Lined by thick layer of glial tissue (astrocytic glia & few thick-walled blood vessels) Gliosis with tendency to infiltrate white matter CSF protein content low unless tumour is the cause

Clinical Features

Varies according to the age at presentation & cause of syringomyelia

Classical Triad

Dissociative anaesthesia typically in cape distribution Muscle wasting & reduced DTR in UL Thoracic kyphoscoliosis Cervical & occipital pain very common

Cervicothoracic

Dissociate sensory loss in arms & trunk Weakness & wasting in upper limbs Intrinsic wasting common Fasiculations & clumbsiness in hands common Absent DTR Absent abdominal reflexes Can see spastic lower limbs Bladder & bowel usually normal

Lumbar

Dissociative lumbosacral sensory loss Weakness & wasting in legs & pelvic girdle Absent DTR Babinski negative Impaired bladder & bowel function

Cervicomedullary

AKA Syringobulbia Palatal & vocal cord paralysis Dysarthria Nystagmus Dizziness Tongue weakness

Post-Traumatic

2-3% after cord injury In cord-injured paraplegic or quadriplegic Deterioration may be due to syrinx Presents with Pain Numbness Increased muscle weakness Increased spasticity Unilateral ascending myelopathy usual presentation

Investigations

Plain radiography Skull & spine may see Scoliosis Canal widening Basilar invagination Atlanto-occipital fusion Platybasia

MRI

Best investigation to more accurately delineate the cyst

Differential Diagnosis

Amyotrophic lateral sclerosis (motor neurone disease) MS Cervical myelopathy Thoracic outlet syndrome Klippel-Feil syndrome Cord tumour Brainstem infarct

Treatment

Indications for intervention Rapid neurological progression Short history Respiratory compromise Pseudobulbar palsy Pre-spinal corrective surgery

Syrinx is best shunted

Syringo-vestibular/ cisternal Syringo-peritoneal Arnold-Chiari malformation may require posterior fossa exploration Suboccipital decompression C1-C2 laminectomy

Significant complications can occur

Haemorrhage Infection Increased neurological deficit Nocturnal respiratory depression

Orthopaedic Implications

1. Pain Usually extremities Headache common that ↑ with cough or sneeze Can occur in neck/ shoulder/ upper arm & resemble rotator cuff pathology or neuritis Backache common

2. Charcot Joints

Syrinx most common cause of upper limb Charcot joints Shoulder & elbow most common Hot swollen joint may be first presentation of syrinx Differentiate from Infection Peripheral neuropathy DM Leprosy Myelomeningocoele Tabes dorsalis Meyer et al 1952 25% of patients with syrinx had Charcot joint With 80% occurring in upper limb

3. Bone Deformity

Skull Basilar invagination common 55% of patients (West & Williams 1979) Neck Short neck with low hairline common Atlanto-axial congenital fusions seen Canal widened If > 1.5x body width on lateral then syrinx likely Scoliosis Commonest first presentation of syrinx 4% of patients with scoliosis have syrinx 20% males with scoliosis have syrinx cf. 2% females Related to posterior column dysfunction & atrophy of the dorsomedial & ventrolateral spinal nuclei Curve appears as Thoracic adolescent curve BUT Often left side thoracic Males > Females Level corresponds with syrinx Often no neurological deficit except Axillary sensation absent Abdominal reflexes absent Treatment Must correct syrinx first Malignant progression if syrinx untreated Prognosis similar to idiopathic once syrinx treated Limb Deformities Upper limb may see late changes Extension at MCPJ with intrinsic wasting & trophic changes “Morvan’s Syndrome” – resorption of terminal digits Pes cavus & clawing in lower limbs
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