In 1891 and 1896, Chiari described various anatomic patterns of herniation of the brain stem through the foramen magnum [23]. The Chiari II malformation, also known as the Arnold–Chiari malformation, is characterized by the displacement of the medulla oblongata into the cervical canal and an upward course of the cervical nerve roots. Almost all children born with myelomenigocele will have the Chiari II malformation which can cause periodic stridor, apnea, swallowing difficulties, upper extremity paresis, hypertonia, nystagmus, and opisthotonis. The symptoms are worse in early childhood. In most affected children treatment of the secondary hydrocephalus with a ventriculoperitoneal shunt will alleviate the symptoms, but in some a decompression of the posterior fossa will be necessary.

The Arnold–Chiari malformation obstructs the cerebral spinal fluid circulation. At birth, the open communication between the fourth ventricle and the central canal allows for decompression of the cerebrospinal fluid into the myelomeningocele sac. Once the sac is closed, this avenue of decompression is lost and hydrocephalus occurs. A ventriculoperitoneal shunt has been the standard treatment to avoid cortical damage, though recently endoscopic third ventriculostomy alone or in combination with choroid plexus cauterization has shown promise as a better treatment option [98, 99].

Hydrocephalus frequently recurs secondary to shunt malfunction. In children, the clinical signs of acute hydrocephalus are bulging fontanelles, altered mental status, nausea, vomiting, and severe headaches [65]. Hydrosyringomyelia may occur when the cerebral spinal fluid pressure within the central canal increases. Symptoms include increasing lower extremity weakness, spasticity, back pain, rapid progression of scoliosis, and upper extremity weakness. Early correction of hydrocephalus by shunt revision is usually curative.

The spinal cord is considered tethered when the conus medullaris is located at an abnormally distal level and fixed there by an inelastic structure. In the child with myelomeningocele, the spinal cord is tethered not by an expendable and easily resected thickened filum terminale, but by an adherence between the neural placode, the surrounding tissues, and the repaired dural layer. These children may also have dermoid inclusion cysts that add to the tethering or cause pressure on adjacent neural tissue. Most children who have undergone operative closure of a myelomeningocele will demonstrate a low lying spinal cord on magnetic resonance imaging (MRI) examination. In these individuals, the diagnosis of the tethered cord syndrome requires the presence of both anatomic tethering and neurological deterioration, and the absence of other causes of deterioration such as hydromyelia, shunt malfunction, and symptomatic Chiari II malformation. An MRI assessment will define the nature of the tether and assess the presence of possible associated pathologies including diastematomyelia, lipomas, dermoids, granulomas, inclusion cysts, and teratomas [37, 76].

Neurological deterioration due to a tethered cord will occur in up to 30 % or more of children with repaired myelomeningocele [90]. Release should be performed before major functional loss occurs. Although the conus level does not significantly change after detethering [17], the procedure can be expected to produce improvement or stabilization in most cases as illustrated by a comparison of outcomes in two long-term studies of sacral level myelomeningocle populations. In patients that had detethering procedures, none of 62 lost ambulatory ability and 61 were community ambulators [92]. In another similar study of 36 patients that did not have routine untethering, one-third had gait deterioration, 11 became wheelchair-dependent, and spinal deformities and lower extremity contractures developed in 44 % [16]. Results from untethering seem to vary with respect to the symptoms. The results are excellent for improvement of pain and motor deficits [54], but less successful for urological functional [20, 52] and accordingly timely intervention is key.

In properly selected myelomeningocele patients, tethered spinal cord release can stabilize a progressive scoliosis. Pierz et al. evaluated the effect of tethered cord release on scoliosis in 21 myelomingocele patients. Three had improvement in the curvatures, and six stabilized. Twelve patients progressed greater than 10°. Eighty-six percent of patients with initial curvatures over 40° and 100 % of those with a thoracic level required spinal fusion [72]. McLone et al. reported on 30 patients with myelomeningocele and scoliosis. In patients with curvatures greater than 50°, 1 out of 6 improved, while 14 of 23 with less severe curvatures stabilized [53].

Allergy to latex rubber has been reported in up to 28 % of individuals with myelomeningocele [10, 21, 51, 56, 58, 94]. These are IgE-mediated reactions characterized by urticaria, bronchospasm, rhinoconjuntivitis, laryngeal edema, and systemic anaphylaxis. The risk factors for intraoperative anaphylaxis are number of surgeries and atopic predisposition [32, 33, 39, 43, 63]. In the past, an attempt was made to identify latex-sensitive patients, but this strategy proved inefficient. A negative history for reaction does not eliminate the possibility of intraoperative anaphylaxis; skin testing lacks sensitivity and safety; and preoperative prophylaxis is not dependable. Accordingly, the present recommendation is that all myelomeningocele patients be treated in a latex-free environment.

Holzman, Gerber, and others have reported successful reoperation in patients that had previous anaphylactic reoperation by perioperative latex avoidance alone [14, 31, 40]. Additionally, a latex-free environment may diminish the number of myelomeningocele patients that become sensitized [64].

Precocious puberty in girls with myelomeningocele is common. Proos et al. noted breast development by age 9 and related the risk of precocious puberty to increased intracranial pressure and shunt malfunction [74]. Furman and Mortimer noted that affected girls began menstruation at an average age of 10 years 3 months and earlier than their mothers and siblings [28].

Spinal deformity occurs commonly and early in children with myelomeningocele. Piggott noted a 90 % incidence of some form of spinal deformity by age 10 years, and in half the patients the curvature was significant enough to merit surgical treatment [73]. The common deformities are scoliosis and hyperkyphosis which are often classified as congenital and developmental. Congenital deformities include scoliosis and kyphosis due to failure of formation or segmentation, and the rather unique form of kyphosis found in the myelomeningocele population due to dysplastic posterior elements. Developmental curvatures occur without vertebral malformation presumably due to muscle paralysis, muscle malposition, or hip deformity and pelvic obliquity [73, 75]. More recently, hydrocephalus, syringomyelia, and spinal cord tethering have been appreciated as causative factors. Spondylolisthesis has also been reported [42, 88].

Problems caused by spinal deformity include recalcitrant ulcerations over the gibbus in individuals with kyphosis or of the ischium or sacrum in wheelchair sitters with scoliosis and trunk imbalance. Pulmonary compromise can occur with significant scoliosis or kyphosis. Those with trunk imbalance in either the sagittal or frontal plane may need to use their hands for support and in doing so lose upper extremity function [6, 38, 41, 81]. Scoliosis is the most common deformity and will be discussed. Kyphosis is covered elsewhere in this text.