Syringomyelia is a disorder of the spinal cord characterized by the development of an abnormal fluid-filled cavity — called a syrinx — within the spinal cord parenchyma or central canal, caused by disrupted cerebrospinal fluid (CSF) circulation that redirects fluid into the cord under pressure. Unlike myelitis, which involves inflammatory destruction of spinal cord tissue, syringomyelia results from a mechanical, hydrodynamic process where CSF is forced into or becomes trapped within the cord substance, progressively expanding and compressing surrounding neural tissue from within. The underlying mechanism involves obstruction of normal CSF outflow at the craniocervical junction or along the spinal canal, most commonly due to Chiari malformation type 1 (CM-1), but also from spinal cord tumors, arachnoiditis, trauma, or tethered cord syndrome. The condition may be congenital or acquired; the congenital form is most often associated with Arnold-Chiari syndrome (Q07.00-Q07.02), while acquired forms include post-traumatic, inflammatory, and idiopathic etiologies (all coded G95.0). The syrinx most frequently involves the cervical and thoracic spinal cord and classically produces a cape-like dissociated sensory loss — loss of pain and temperature with preserved light touch — due to damage to the crossing spinothalamic fibers at the center of the cord, before progressing to motor weakness, spasticity, and autonomic dysfunction. syringomyelia is commonly confused with hydromyelia — a dilation of the central canal itself lined by ependymal cells, considered a less destructive variant — though both are classified under G95.0 and treated similarly in ICD-10-CM.
The word entered English in the 1870s as syringomyelia (noun), coined in New Latin from Greek syrinx (“pipe, tube”) + myelos (“marrow, spinal cord”) + -ia (condition) — literally “a tube-like condition of the spinal cord.” The root syrinx (“pipe or tube”) connects Syringomyelia to the entire syring- root family: syringosubarachnoid (syrinx + subarachnoid space → shunt procedure), syringobulbia (syrinx extending into the brainstem/bulb), and syringe (tube used to inject or withdraw fluid). The combining form myel- appears extensively in medical terminology: myelopathy, myelitis, myelomeningocele, demyelination, and myelography.
🔀 ALIASES / ALTERNATE TERMS
Syringomyelic(adjective form — used in collocations such as “syringomyelic syndrome,” “syringomyelic cavity,” “syringomyelic dissociation”)
Syrinx(clinical synonym for the fluid-filled cavity itself; used interchangeably in neurosurgery and neurology documentation; coded G95.0)
Hydromyelia(dilation of the central canal by CSF lined by ependymal cells; considered a lesser/early form; classified under G95.0 in ICD-10-CM; distinguished from true syringomyelia by ependymal lining)
Communicating syringomyelia(subtype with direct communication between syrinx and central canal; associated with Arnold-Chiari syndrome — Q07.00)
Non-communicating syringomyelia(subtype isolated from central canal; typically post-traumatic or tumor-related; also coded G95.0)
Syringobulbia(extension of the syrinx into the brainstem/medulla oblongata; causes cranial nerve deficits and dysphagia; coded G95.0)
Post-traumatic syringomyelia(acquired form following spinal cord injury; develops months to years after trauma; sequela coding requires underlying spinal cord injury code as principal diagnosis)
Idiopathic syringomyelia(no identifiable underlying cause; no Chiari, no trauma, no tumor; coded G95.0 as primary diagnosis)
Chiari-associated syringomyelia(most common form; requires dual coding of Q07.00 for the Chiari malformation plus G95.0 for the syrinx)
Hydromyelia — a dilation of the central canal proper lined by ependymal cells; considered a milder, often congenital variant of the same CSF-accumulation spectrum; distinguished from syringomyelia by the presence of the ependymal lining and direct communication with the ventricular system
Syringobulbia — shares the syring- root; upward extension of the syrinx cavity into the medulla oblongata; produces cranial nerve signs including dysarthria, dysphagia, and nystagmus; coded G95.0
Chiari malformation — the most common cause of syringomyelia; cerebellar tonsillar herniation through the foramen magnum obstructs CSF outflow; coded Q07.00 (without spina bifida or hydrocephalus)
Arachnoiditis — inflammatory scarring of the arachnoid membrane surrounding the spinal cord; a recognized cause of acquired syringomyelia by obstructing CSF flow
Myelitis — inflammatory destruction of spinal cord tissue; distinguished from syringomyelia by its immune-mediated etiology vs. mechanical/hydrodynamic mechanism; excluded from G95.0 per ICD-10-CM Excludes2 note
Tethered cord syndrome — abnormal attachment of the spinal cord limiting its movement; can cause secondary syrinx formation by altering CSF dynamics
cerebrospinal fluid — the fluid whose abnormal circulation is the primary driver of syrinx formation; disrupted CSF flow at any level can redirect fluid into cord parenchyma
spina bifida — congenital neural tube defect frequently co-occurring with Chiari II malformation and syringomyelia; coded separately from G95.0
Dissociated sensory loss — hallmark clinical finding in syringomyelia; loss of pain and temperature sensation (spinothalamic) with preserved light touch (dorsal column), classically in a cape-like distribution over shoulders and arms
Intramedullary spinal cord tumor — both a cause of secondary syringomyelia and a key differential diagnosis; MRI is essential to distinguish tumor-associated cyst from idiopathic syrinx
MRI spine — primary diagnostic imaging modality for syringomyelia; cine MRI adds dynamic CSF flow assessment; the gold standard for detecting syrinx size, extent, and progression
CODING CORNER
🏥 ICD-10-CM CODES
Primary Code | Syringomyelia & Syringobulbia (G95.0 — Single Billable Code, No Laterality)
Laminectomy with drainage of intramedullary cyst/syrinx to peritoneal or pleural space — syringoperitoneal shunt; used when subarachnoid shunting is not feasible
Therapeutic exercises; 15 min — neuromuscular re-education and strength maintenance in patients with syrinx-related motor deficits
⚠️ Coding Note:G95.0 is a single billable code covering all forms of syringomyelia — idiopathic, communicating, non-communicating, cervical, thoracic, and syringobulbia extension — with no laterality or site specificity required, which is unusual for a spinal cord condition. When the syrinx is secondary to Chiari malformation, sequence the Chiari code (Q07.00-Q07.03) first as the underlying etiology per ICD-10-CM conventions, followed by G95.0 as the manifestation. For post-traumatic syringomyelia, the spinal cord injury sequela code (e.g., S14.109S, S24.109S) should be sequenced before G95.0 to reflect the cause-and-effect relationship; failure to add the sequela code on inpatient profee claims is a common undercoding pattern — trigger phrase to watch: “progressive neurological changes after prior SCI” or “late-onset myelopathy following spinal trauma.” On inpatient profee claims, if the physician documents a syrinx without specifying syringomyelia or syringobulbia by name, that documentation is sufficient to support G95.0 per ICD-10-CM guidance — query if only “spinal cyst” or “intramedullary cyst” is documented, as those may map to G95.89 instead. Modifier -62 (Co-surgery) may apply when two surgeons of different specialties (e.g., neurosurgeon + spine surgeon) collaboratively perform posterior fossa decompression with syringosubarachnoid shunting; modifier -22 applies to 63172 when the procedure requires significantly increased work due to prior surgery, dense adhesions, or complex anatomy.