spina bifida is a congenital neural tube defect resulting from incomplete closure of the caudal neuropore during embryonic development — typically between days 26-28 after conception — in which the vertebral arches fail to fuse, leaving the spinal cord and/or meninges exposed or herniated through the defect. It exists on a clinical spectrum from the benign spina bifida occulta (Q76.0), an incidental radiologic finding with no herniation, to the severe open cystic forms — meningocele (meninges herniate but spinal cord is intact) and myelomeningocele (both spinal cord and meninges herniate through the defect), classified under Q05.0-Q05.9 by anatomic level and presence or absence of hydrocephalus. The underlying pathophysiology involves a “two-hit” mechanism: the primary structural malformation disrupts motor, sensory, and autonomic neural pathways below the lesion level, while secondary injury from amniotic fluid chemical irritation and mechanical trauma throughout gestation worsens neurologic outcomes — the rationale behind fetal surgery (MOMS trial). Spina bifida cystica (myelomeningocele) is pathological by definition; spina bifida occulta may be physiological/incidental in up to 10-20% of the general population. Clinically relevant subtypes include cervical (Q05.0/Q05.5), thoracic (Q05.1/Q05.6), lumbar (Q05.2/Q05.7 — most common), and sacral (Q05.3/Q05.8); codes Q05.0-Q05.4 are used when hydrocephalus is present (combination codes — do not separately assign Q03.9 or G91.x for the same hydrocephalus), while Q05.5-Q05.9 are used when hydrocephalus is absent. Spina bifida is commonly confused with spina bifida occulta (Q76.0) — the key difference is that occulta involves only incomplete vertebral arch fusion with intact overlying skin and no herniation of neural tissue, does not map to HCC 194 in CMS-HCC v28, and is classified under Q76 not Q05.
Latin findere (FIN-deh-reh), past participle fissus
”to split,” “to cleave” — verb-derived adjectival suffix meaning “cleft” or “divided”; Adjective-forming suffix — “split into”
The term entered English in the 1690s as spina bifida (noun phrase), borrowed directly from Modern Latin spina bifida, coined by the Dutch anatomist Nicolaas Tulp — literally “cleft spine” or “split backbone.” The adjective bifida is the feminine form of bifidus (from bi- + findere), agreeing with the feminine Latin noun spina. The root findere (“to split”) connects Spina Bifida to the broader -fida / fissure root family: fissure (fissura → cleft or groove), bifurcation (bi- + furca → splitting into two branches), and nuclear fission (fission → act of splitting). The prefix bi- is highly productive in medical terminology, appearing in bilateral , bicuspid , binocular , and bifocal .
🔀 ALIASES / ALTERNATE TERMS
Myelomeningocele (MMC)(most severe open form; spinal cord + meninges herniate through vertebral defect; universal neurologic deficits below lesion level; classified under Q05.x by level — the predominant form encountered in inpatient profee coding)
Meningocele(meninges herniate but spinal cord remains in situ within the sac; generally fewer neurologic deficits than MMC; also classified under Q05.x per lesion level)
Spina bifida occulta(incomplete vertebral arch fusion with intact overlying skin and no herniation; incidental imaging finding; classified under Q76.0 — NOT under Q05; does not carry HCC 194 mapping)
Rachischisis(complete cleft of the spinal column; severe open form often used interchangeably with myeloschisis; ICD-10-CM includes under Q05 category)
Spina bifida cystica / aperta(clinical synonyms for open/cystic forms including meningocele and myelomeningocele; “aperta” = open; coded Q05.0-Q05.9)
Hydromeningocele(meningocele filled with CSF; included under Q05 category)
Syringomyelocele(form of MMC in which dilated central canal of cord protrudes into the sac; included under Q05 Includes notes)
Myelocele(open neural plate exposed directly to surface without a sac covering; severe open form; included under Q05 category)
Lipomyelomeningocele / Lipomeningocele(closed spinal dysraphism with fatty spinal tumor and cord tethering; a variant of spina bifida occulta spectrum; associated with Q06.8 tethered cord)
Occult spinal dysraphism(broader term for closed/occult forms including spina bifida occulta and lipomyelomeningocele; Q76.0 or Q06.8 depending on features)
Open neural tube defect (NTD)(umbrella clinical term used in prenatal counseling and CDI documentation; maps to Q05.x for spinal forms)
spina bifida Occulta — the occult/hidden form of spina bifida classified under Q76.0; distinguished by intact overlying skin, absence of neural tissue herniation, and generally incidental discovery on imaging; does NOT carry the same clinical severity, HCC mapping, or MS-DRG weight as open forms under Q05.x
Myelomeningocele — the most severe and common open form of spina bifida; the spinal cord and meninges protrude through the vertebral defect; defines the classic clinical picture with paraplegia, neurogenic bladder, and hydrocephalus; classified Q05.0-Q05.9 by level
Arnold-Chiari Malformation Type II — virtually universal comorbidity in myelomeningocele patients; downward herniation of the cerebellar vermis and brainstem through the foramen magnum; classified Q07.01 (with spina bifida), Q07.02 (with hydrocephalus), or Q07.03 (with both); Excludes1 note under Q05 — do not double-code without reviewing sequencing
Tethered Spinal Cord Syndrome — fibrous anchoring of the conus medullaris below L2; may co-occur with spina bifida or present independently; coded Q06.8; surgical detethering CPT 63200
hydrocephalus — accumulation of CSF causing ventricular dilation; present in ~80-90% of lumbar myelomeningocele patients; when congenital and associated with spina bifida, captured as a combination code in Q05.0-Q05.4 — do not separately assign Q03.x; acquired hydrocephalus coded G91.0 (communicating) or G91.1 (obstructive)
syringomyelia — fluid-filled cyst within the spinal cord; common secondary complication of Chiari II or tethered cord; coded G95.0; report additionally with Q05.x when documented
Neurogenic Bladder — disruption of sacral micturition center input causing overactive (N31.0) or flaccid (N31.2) bladder dysfunction; universal in lumbosacral MMC; code additionally with Q05.x per “Use additional code” tabular instruction
Neurogenic Bowel — disruption of colorectal motility and sphincter control; coded K59.2; code additionally with Q05.x
Paraplegia — complete loss of voluntary motor function below the level of the spinal lesion; coded G82.20 (unspecified), G82.21 (incomplete/paraparesis), or G82.22 (complete); required additional code per Q05 “Use additional code” instruction when documented by the provider; maps to HCC 224 in CMS-HCC v28
Diastematomyelia — split cord malformation; spinal cord divided by a bony or fibrous septum; frequently co-occurs with spina bifida; coded Q06.2; report as additional code
Anencephaly — failure of closure at the cephalic neuropore (head end of neural tube) rather than the caudal end; coded Q00.0; distinguished from spina bifida by cranial rather than spinal involvement; universally fatal
Encephalocele — herniation of brain tissue and/or meninges through a skull defect; a cranial NTD; coded Q01.0-Q01.9 by site; distinguished from spina bifida by cranial location
Folate Deficiency — primary modifiable risk factor for neural tube defects; coded E53.8; document when present; valproic acid and carbamazepine are folate antagonists that increase NTD risk
MRI of Spine / Brain — primary diagnostic imaging tool for evaluating spina bifida defect level, tethered cord, Chiari malformation, and syringomyelia; required to confirm lesion level for Q05.x specificity
CODING CORNER
🏥 ICD-10-CM CODES
Spina Bifida WITH Hydrocephalus (Q05.0-Q05.4 — Combination Codes; Do NOT Separately Code Hydrocephalus)
Dural graft, spinal — adjunctive to MMC closure when dural grafting performed as separate documented component; report with 63704/63706 when applicable
Neuroendoscopy, intracranial, with fenestration of intraventricular cysts or with third ventriculostomy — endoscopic third ventriculostomy (ETV); alternative to shunt in selected patients
Arthrodesis, posterior, for spinal deformity, up to 6 vertebral segments — scoliosis correction common in spina bifida; pair with appropriate M41.x spinal deformity code
Implantation, revision or repositioning of tunneled intrathecal or epidural catheter for long-term medication administration via implantable pump — intrathecal baclofen pump for spasticity management
Unlisted fetal invasive procedure, including ultrasound guidance, when performed — open fetal surgery MMC repair (MOMS procedure); prior authorization required; document maternal-fetal surgery criteria met
⚠️ Coding Note:Q05.x codes require specificity across two dimensions: (1) anatomic level of the spinal lesion — cervical, thoracic, lumbar, or sacral — and (2) presence or absence of hydrocephalus; when hydrocephalus is captured within Q05.0-Q05.4 as a combination code, do NOT additionally assign Q03.x or G91.x for the same hydrocephalus episode. For sequencing on inpatient profee claims: when the admission is for the congenital condition itself (e.g., initial neonatal repair), Q05.x is the principal diagnosis; when admitted for a complication (e.g., shunt revision, UTI from neurogenic bladder), the complication leads and Q05.x is an additional code. Undercoding alert:paraplegia (G82.20-G82.22) is routinely missed on inpatient profee claims — any documentation containing phrases like “paralysis below lesion level,” “no motor function in lower extremities,” or “complete loss of sensation below T12” should trigger assignment of G82.22 as an additional code, which maps independently to HCC 224 in CMS-HCC v28 and can significantly impact risk-adjusted reimbursement. For CPT surgical coding, the diameter of the myelomeningocele defect (less than 5 cm → 63704 vs. 5 cm or greater → 63706) must be explicitly documented in the operative report — if size is absent, query the surgeon before defaulting to 63704. Q05.9 (unspecified) should be avoided and should trigger a CDI query for lesion level documentation; CMS audit targets for HCC v28 flag Q05.9 as insufficient for HCC 194 capture.