4.2b Craniorachischisis (Q00.1)

Craniorachischisis is a very serious NTD characterized by the combination of anencephaly (absence of the brain and cranial vault, without skin covering) with a contiguous bony defect of the spine (also without meninges covering the neural tissue – rachischisis) (see Fig. 4.3). Spine involvement can be limited to the cervical spine where it might be difficult to clinically differentiate from holoanencephaly. Rarely, the open defect can extend to the thoracic or even lumbosacral spine (craniorachischisis totalis). Craniorachischisis results from failed closure of the anterior neuropore, but the mechanism leading to failure of closure of the contiguous spine is not well understood. In some infants, there is accompanying retroflexion of the spine, which results in a body habitus resembling another rare NTD, iniencephaly (see Fig. 4.5). Because of the early lethality of this condition, many affected fetuses are either stillborn or result in a termination of pregnancy (if prenatally diagnosed and pregnancy terminations are permitted).

Fig. 4.3. Craniorachischisis

Fig. 4.3. Craniorachischisis

Photograph source: CDC–Beijing Medical University collaborative project.

Fig. 4.4. Craniorachischisis with retroflexion

Fig. 4.4. Craniorachischisis with retroflexion

Relevant ICD-10 codes

Q00.1 Craniorachischisis


Prenatal. Craniorachischisis is readily diagnosed using ultrasound. However, it can be confused with other defects involving the brain – anencephaly, acrania or amniotic band syndrome. For this reason, a prenatal diagnosis of craniorachischisis should always be confirmed postnatally. When this is not possible (e.g. termination of pregnancy or unexamined fetal death), the programme should have criteria in place to determine whether to accept or not accept a case based solely on prenatal data.

Postnatal. Careful examination of the fetus or newborn can confirm the diagnosis of craniorachischisis and distinguish it from the other rare anomalies that involve the brain, cranium and spine. In craniorachischisis, the eyes are usually normally formed but tend to bulge as a result of the absent frontal portion of the cranial vault, and the neck might appear to be shortened and is sometimes retroflexed. The craniorachischisis lesion is always open and the spinal lesion is always continuous with the anencephaly.

Clinical and epidemiologic notes

Distinguishing craniorachischisis from other abnormalities of the brain and spinal cord is important because these conditions have different causes and associated anomalies. With careful examination, the diagnosis of craniorachischisis is straightforward. Craniorachischisis is a uniformly fatal condition and is often isolated and non-syndromic. However, the co-occurrence of cleft lip and palate, omphalocele, limb defects, cyclopia or trisomy 18 has been reported in some cases, but no robust populationbased studies have been conducted to understand the proportion of isolated cases or associated anomalies. For this reason, it is very important to report all physical findings and obtain good clinical photographs for the expert reviewer. Craniorachischisis is reported to occur more commonly in females.

Craniorachischisis is a rare defect and is most prevalent in countries with an overall high prevalence of NTDs. Because of the rarity of craniorachischisis, studies of non-genetic risk factors are challenging. Presumably the non-genetic risk factors should be similar to that of other NTDs, including pregestational diabetes, obesity, and hyperthermia (e.g. fever) in early pregnancy, and folic acid insufficiency/deficiency. Adequate periconceptional use of folic acid (as a supplement or through fortification) might also prevent craniorachischisis.

Few reports on NTD prevalence specifically mention craniorachischisis. The reported prevalence varies widely, with estimates ranging between 0.1 to 10.7 per 10 000 live births. Craniorachischisis is counted when calculating total NTD prevalence.


Q00.1 Craniorachischisis


Q00.0 Anencephaly, Acrania, acephaly
Q00.2 Iniencephaly
Q00.20 Iniencephaly, open
Q00.21 Iniencephaly, closed

Checklist for high-quality reporting

Craniorachischisis – Documentation Checklist
Describe in detail:
  • Defect – overall presentation.
  • Extent of spinal involvement (cervical spine or lower) – especially comment on and document the fact that the head involvement (anencephaly) and the spine defect are contiguous, without intervening normal appearing spine.
  • Retroflexion of neck and spine – this is more typical of iniencephaly, so important to note.
  • If amniotic bands are present – disruptions by amniotic bands could possibly mimic severe atypical NTDs.
  • If the spinal lesion and the anencephaly are separated by intact skin, the case would be considered a multiple NTD and not craniorachischisis.
    • Take and report photographs: Show clearly the missing cranium and spine; can be crucial for review.
    • Describe evaluations to find or rule out related and associated anomalies:
        • Orbits – usually protruding but normally developed (do not include as an associated anomaly).
        • Head circumference will be small – do not code as microcephaly.
        • Spina bifida (mention but do not code contiguous defects).
        • Other anomalies or chromosomal abnormality.
        • Iniencephaly (do not code).

Report whether autopsy (pathology) findings are available and if so, report the results.

Suggested data quality indicators

Category Suggested Practices and Quality indicators
Description and documentation
  • Review sample for documentation of key descriptor (absence of skull and brain, not covered by skin; spinal defect).
  • Take and attach photographs – essential for review and correct classification.
  • Report and track proportion of cases among live births, stillbirths and pregnancy terminations.
  • Code as Q00.1 (if anencephaly and open spina bifida are contiguous).
  • Do not code the contiguous spina bifida as a separate defect. Only code if spina bifida is not contiguous with craniorachischisis.
Clinical classification
  • Track proportion of anomalies and syndromes occurring with craniorachischisis. Do not include findings that are a direct consequence of the condition (such as prominent eyes, talipes, etc.).
  • If the fetus was stillborn, or a pregnancy termination performed, check for a pathology report and physical description at delivery.
  • Monitor prevalence – prevalence varies by country/region, country income level and race/ethnicity.