Cranial Meningocele (Types, Causes, Treatment)

Overview

The central nervous system develops from the neural tube. The neural plate is a structure that develops initially on the dorsal aspect of the embryo [1]. With the passage of time, the two edges of the neural plate grow toward each other to form the neural tube. The upper end of the neural tube gives rise to the brain and rest of it forms the spinal cord.

Cranial Meningocele is a neural tube defect that develops due to inadequate development of the upper end of the neural tube. It is characterized by the herniation of membranes of brain through an abnormal bony opening in the cranium or through one of the parietal foramina. In this birth defect the herniated sac consists of only meninges. If the herniated sac consists of brain contents, it is then referred to as encephalocele. Most of the time, these two terms are used synonymously [1,2].

Cranial Meningocele

Types of cranial meningocele

It can be classified into various types depending upon the location. It is also important to know that severity of meningocele varies patient to patient, depending upon its location. The various types are:

  • Occipital meningocele- it is characterized by the presence of a mass on the posterior midline of the cranium. It is the most common type of meningocele.
  • Frontoethmoidal meningocele- it is present in frontoethmoidal region of head.
  • Nasofrontal meningocele-it is in the nasofrontal area of the head.
  • Nasoorbital meningocele-it is in the nasoorbital region.
  • Encephalomeningocele- it is characterized by the protrusion of both brain contents and meninges through a bony defect in the cranium. It is a more dangerous condition in comparison to meningocele [2].

Incidence

Cranial Meningoceles/Encephaloceles are rare neural tube defects, occuring at the rate of one per 5000 live births worldwide. Posterior midline meningoceles are more common in Europe and North America.  Frontal meningoceles are more commonly seen in Southest Asia, Africa, Malaysia and Russia. These Neural tube defects (NTDs) develop in families with a history of spina bifida [3,4].

Causes and risk factors

The incomplete closure of the upper end of neural tube during embryogenesis results in cranial meningocele/encephalocele. The exact cause is not known, but there are certain factors, which are believed to be associated with the occurrence of it. Studies reveal that low levels of folic acid, vitamic C and riboflavin during early pregnancy (first trimester) are associated with central nervous system malformations. Risk factors of it are given below:

  • Exposure of the pregnant lady to teratogens (substances considered to cause birth defects)
  • Exposure to tryptan blue (a stain used to dye dead tissues or cells)
  • Exposure to arsenic
  • Folic acid deficiency
  • Family history of Neural Tube Defects (NTDs)
  • Some viral infections like rubella or cytomegalovirus, etc
  • Diabetes
  • Maternal obesity and smoking [4,5]

Clinical presentation

This medical issue can be presented with a swelling and groove down the middle of the skull, or between the forehead and nose or on the posterior aspect of cranium. This cranial abnormality may also be associated with craniofacial abnormalities or other brain malformations [6]. Other clinical features are:

  • Development of hydrocephalous- characterized by macrocephaly, headache, vomiting, urinary incontinence, Bradycardia, hypertension and irregular respiration. It is present in almost 80% of the cases of cranial meningocele.
  • Spastic weakness of all four limbs
  • An abnormally small sized head.
  • Uncoordinated muscle movements
  • Delayed developmental milestones
  • Vision problems
  • Mental and growth retardation
  • Seizures [6,7]

Diagnosis

Usually cranial meningoceles/encephaloceles are easily identifiable deformities and are diagnosed immediately after birth, but a small cranial meningocele/encephalocele in the nasal or forehead region can go undiagnosed. The presence of various physical and developmental delays in the child can indicate the presence of encephaloceles. Prenatally these defects can be diagnosed by following tests:

  • Serum Alpha Fetoprotein (AFP) levels
  • Quadruple/triple screen
  • Ultrasonography
  • Amniocentesis [8,9]

Treatment

The best treatment for it is surgical repair. Surgical repair can be carried out before or after birth. Prenatal surgery has better outcomes than that of postnatal. Prenatal fetal surgeries may include:

  • Open fetal surgery
  • Minimal invasive fetal surgery [10]

Post-natal surgery is usually performed during infancy. The extent of surgical correction depends on the location and size of the it; however, large protrusions can be removed without causing major disability. The goals of surgery include:

  • Repositioning the bulging area back into the cranium
  • Removing  the protrusions
  • Correcting the deformities and typically relieving intracranial pressure that may delay normal brain development.
  • Placing a shunt if needed [5]

Conclusion

Cranial meningocele is a rare type of NTD, the exact cause of which is still a uncertain. Usually it can be identified visually afterbirth. Surgical repair is the treatment of choice for it. Prognosis depends upon the contents of herniated sac. The presence of brain tissue in the sac is associated with significant mortality (44%) and with impaired cognitive development (91%). In order to avoid the complications of these defects early diagnosis and prompt management are necessary.

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References

  1. Shallow TA. Spina bifida and cranial meningocele. Ann Surg 1928; 87(6): 811-22.
  2. Simpson DA ,David DJ, White J. Cephaloceles: treatment, outcome, and antenatal diagnosis. Neurosurgery 1984;15(1):14-21.
  3. Laurence KM, Tew BJ. Natural History of Spina Bifida Cystica and Cranium Bifidum Cysticum. Arch Dis Child 1971; 46(246): 127-38.
  4. Copp AJ, Stanier P, Greene ND. Neural tube defects: recent advances, unsolved questions, and controversies. Lancet Neurol 2013;12(8):799-810.
  5. Manning SM, Jennings R, Madsen JR. Pathophysiology, prevention, and potential treatment of neural tube defects. Ment Retard Dev Disabil Res Rev 2000;6(1):6-14.
  6. McComb  JG. Spinal and cranial neural tube defects. Semin Pediatr Neurol 1997;4(3):156-66.
  7. Saboval L,Horn F, Drdulova T, et al. [Clinical condition of patients with neural tube defects]. Rozhl Chir 2010;89(8):471-7.
  8. Imbruglia L, Cacciatore A, Carrara S. Abnormal skull findings in neural tube defects. J Prenat Med 2009; 3(3): 44-7.
  9. Main MD, Mennuti MT. Neural tube defects: issues in prenatal diagnosis     and counselling. Obstet Gynecol 1986;67(1):1-16.
  10. Deprest JA, Devlieger R, Srisupundit K, et al. Fetal surgery is a clinical    reality. Semen Fetal Neonatal Med 2010;15(1):58-67.