Syringomyelia (ORPHA:3280)
A rare medullar disease characterized by cerebrospinal fluid (CSF)-filled cavities (syrinx) inside the spinal cord as a result of an obstruction to CSF flow, either at the craniovertebral junction (Chiari malformation) or in the perimedullary subarachnoid spaces (arachnoiditis).
Epidemiology
Estimated prevalence is 8.4/100,000. Cases of autosomal recessive familial syringomyelia have been reported with an estimated incidence of 2% of all syringomyelia cases.
Clinical description
Although syringomyelia can lead to disruption of neural connections in the spinal cord and to neurological damage, 50% of patients (when all types of syrinxes are considered) will experience no or only mild disability. In symptomatic patients, onset is usually marked by pain and sensory disturbances, varying from complete absence of sensation, pins and needles or temperature sensing alterations, to increased sensation to stimuli. Although there are no clear clinical clues at neurological examination, a 'cape-like' sensory dissociation (loss of the ability to distinguish between hot and cold with intact light-touch sensation in the upper limbs and torso), as well as reduced upper limb reflexes, are quite specific initial findings when present. Motor symptoms usually range from varying degrees of weakness to spasticity and loss of autonomy. Alterations in bladder and sexual function may also be present.
Etiology
Syringomyelia is due to obstruction of CSF flow either at the craniovertebral junction (e.g. Chiari malformation) or in the perimedullary subarachnoid spaces (e.g. arachnoiditis). Chiari malformations can be associated with other craniovertebral junction malformations (e.g. basilar invagination) or neural tube defects (Chiari II malformation). Spinal arachnoiditis can be either idiopathic or secondary (postinfectious, posttraumatic, posthemorrhagic, postoperative).
Diagnostic methods
Neurological examination and MRI are required for diagnosis. MRI is the gold standard and reveals a fluid filled cavity with variable degrees of vertical and horizontal extension within the spinal cord ranging from involvement of one level up to extension over the entire spinal cord. The signal characteristics on MRI are usually quite similar to those of CSF.
Differential diagnosis
The differential diagnosis includes persistent or dilated central canal (hydromyelia, slits), myelomalacia, tumoral cysts, myelitis, amyotrophic lateral sclerosis and multiple sclerosis.
Management and treatment
Management consists of long-term follow up and surgery in cases of progressive neurological deterioration. The goal of surgery is to restore CSF flow either at the craniovertebral junction in case of Chiari malformation (foramen magnum decompression) or in the perimedullary subarachnoid spaces in case of arachnoiditis (arachnoidolysis). If not possible, or in case of failure, a shunting procedure can be performed to drain the syrinx, either to the peritoneal space (syringoperitoneal shunt) or pleural space (syringopleural shunt).
Prognosis
Around 50% of Chiari malformation type I patients with syringomyelia remain neurologically stable. In cases with progressive deterioration, surgical intervention usually prevents clinical progression. In cases of posttraumatic syringomyelia due to spinal cord compression, reconstruction of the spinal canal appears to yield similar results. Prognosis is worse for cases in which the only surgical option is direct shunting of the syrinx, as this often leads to neurological deficit and recurrence. Persistent or dilated central canal, which is not a syringomyelia, has a benign natural history with usually no progression neither clinically nor radiologically.

                            Last update: 
                            December 2023


                            - Expert reviewer(s): 
                            Dr Steven KNAFO  - Dr Silvia MORAR