Together, anencephaly, encephalocele and myelomeningocele have a total incidence of one in 1000 births in Switzerland; the incidence of minimal spinal dysraphism is at least one forth of the above mentioned CNS anomalies.

1. In contrast to the common dysraphism, the incidence of which is decreasing due to a preconceptional prophylaxis with folic acid and mainly due to prenatal ultrasound, minimal spinal dysraphism is of major clinical significance today.
2. In spite of minimally visible findings on the back, intraspinal malformations may be present which, if not treated, lead to progressive neurological deficits during growth.
3. Usually, no prenatal diagnosis is possible by ultrasound, and even postnatally this type of dysraphism is often not recognized if not considered as cause of neurological deficits.

The etiology is almost the same as in myelomeningocele, with a combination of familial predisposition and external injury during early pregnancy by noxious factors.

a) Lipomeningocele. Isolated intraspinal lipoma.
b) Hypertrophic filum terminale, arrested ascent of the spinal cord.
c) Dural adhesions of the conus.
d) Intradural sinus without/with intradural epidermoid or dermoid cyst.
These main types are often combined; in addition, diastematomyelia, anterior myelomeningocele, spina bifida and other vertebral anomalies and of the sacrum may occur.

The primary malformation leads to a chronic progressive or acute neurological deficit during growth or following a trauma due to compression and/or traction of the conus.

In more than 2/3 of cases, recognizable findings in the lumbosacral region are observed; these cutaneous malformations may indicate mild forms of spinal dysraphism, needing further evaluation.
The orthopaedic findings and neurological deficits concern asymmetrically the legs, buttock and/or the back, and are often not present from the beginning.
Examples are a unilateral foot deformity or backache; in addition, atrophy of single muscles or signs of spasticity. Likewise, disturbance of voiding and defecation may be observed with urine incontinence and constipation.

With increasing age most patients become symptomatic either following the neonatal period at the earliest, or during adulthood at the latest.
In the single case no prognosis is possible. Unawareness of the disease carries the risk that each symptom and sign is treated by a different specialist, e.g. an incontinence by a pediatric urologist, or a foot deformity by an orthopedist.

The differential diagnosis depends on the externally recognizable findings at the back, and the neurological deficits.
It includes mainly a simple dermal sinus at the level of the coccyx, a sacrococcygeal teratoma, a myelomeningocele without or with lipoma, and a meningocele.

In case of externally recognizable findings in the lumbosacral region, a precise history of micturation and defecation, and orthopedic and neurological clinical examinations are necessary, as well as x-rays of the vertebral column and sacrum.
In newborns, ultrasound of the lumbosacral region and the spinal cord is indicated.
Beyond the neonatal period, and later in life, MRI is indicated for confirmation and description of the suspected minimal spinal dysraphism.
In case of confirmation of a suspected mild form of spinal dysraphism with or without neurological deficit: in addition, urodynamic studies and anorectal manometry with urological and anorectal (functional) x-rays, and in case of neurological deficits, neurological laboratory examinations should be performed.
These examinations may also be used on follow-up.

If the diagnosis of minimal spinal dysraphism without/with neurological deficit is confirmed, a surgical revision is indicated: Removal of the anomalies leading to compression and traction (tethering) of the spinal cord, and of the other anomalies, e.g. dermal sinus and dermoid cyst with the danger of ascending meningitis and intradural abscess.
Surgery is performed with magnification and monitoring of the functions of the conus, and requires knowledge of the possible abnormalities.
In case of neurological deficit, non-operative and operative measures of rehabilitation are necessary, e.g. physiotherapy and tendon transfer, clean intermittent catherization, and antibiotics.

It seems that asymptomatic infants operated on in the first three months of life remain so. In symptomatic cases the findings remain stable in 2/3 of the cases following surgery, and 1/3 either ameliorate or become worse.