Intranasal Meningoencephalocele

Introduction

Nasal meningoencephalocele is also known as encephalocele or cephalocele. Nasal meningoencephalocele involves herniating cranial contents into the nose through a skull-based defect. These encephaloceles can consist solely of meninges (meningoceles) or brain tissue (meningoencephaloceles). Myelomeningocele, meningocele, encephalocele, and anencephaly make up 80 % of all neural tube defects (NTDs), with encephaloceles accounting for 15% to 20% of these cases. The incidence of congenital encephaloceles is estimated at 1 in 10,000 live births. However, the actual incidence is likely higher due to many pregnancies being terminated when encephaloceles are diagnosed in utero.

What Is the Incidence Of Intranasal Meningoencephalocele?

The incidence remains high in developing countries. Globally, the prevalence of NTDs is about 180 per 100,000 live births, but in Ethiopia, it is 630 cases per 100,000 children, with a prevalence of 10 encephaloceles per 100,000 children. Many NTDs show a predominance in females, which is especially pronounced for encephaloceles (4.5:1). Female patients are more likely to have occipital encephaloceles (1.9:1) compared to anterior encephaloceles, which are more common in male patients. However, some studies report similar incidences of anterior encephaloceles in both sexes.

Approximately 70% to 90% of encephaloceles are in the occipital area. Anterior encephaloceles are more frequently seen in Asia, Africa, and Russia, with 1 case in 3,500 to 6,000 live births, compared to North America and Europe, where the incidence is 1 case in 35,000 live births. In India, the prevalence of occipital encephaloceles varies, with some reports indicating a prevalence of 60% and others as low as 26%. Neurological problems are more common in posterior encephaloceles. Incidental temporal lobe/middle cranial fossa pit defects can be found in up to 22.2% of internal auditory canal imaging examinations, with 5% forming an encephalocele.

What Are the Causes Of Intranasal Meningoencephalocele?

Most encephaloceles are congenital, but some can develop due to tumors, trauma, or iatrogenic injury. A widely accepted theory for the origin of congenital encephaloceles is the incomplete separation of the surface ectoderm from the neuroectoderm after the neural folds close. The cranial neuropore typically closes on the 25th day of embryogenesis; issues occurring before this day can result in an incomplete closure with a defect not covered by skin. Both genetic and environmental factors contribute to the development of encephaloceles. TORCH infections (toxoplasma, rubella, cytomegalovirus, herpes simplex) have been implicated in many cases. Consanguineous marriages and previous pregnancies with neural tube defects (NTD) are also contributing factors.

Over 30 syndromes have been linked to encephaloceles, including Meckel-Gruber syndrome, Walker-Warburg syndrome, Fraser syndrome, Knobloch syndrome, Roberts syndrome, morning glory syndrome, and amniotic band syndrome. The relationship between maternal folate use and the incidence of encephaloceles remains unclear.

What Are the Symptoms Of Intranasal Meningoencephalocele?

The following are the symptoms of intranasal meningoencephalocele:

• Watery nasal discharge.

• Cerebrospinal fluid (CSF) rhinorrhea.

• Increased nasal discharge flow.

• Nasal obstruction.

• Headache.

• Vision loss.

• Hypertension (high blood pressure).

How To Diagnose Intranasal Meningoencephalocele?

A visible, skin-covered mass near the midline of the head, either in the anterior or posterior area, indicates an encephalocele. Anterior encephaloceles typically involve the nasal bridge, glabella, or medial orbit, while posterior encephaloceles can be found above or below the torcula. The sac may be mostly filled with cerebrospinal fluid (CSF) and can be translucent. The size of the encephalocele can cause significant facial deformity and hypertelorism. Generally, patients maintain good vision.

Encephaloceles involving the intranasal area can cause nasal obstruction, snoring, CSF leaks, or meningitis. Very large posterior encephaloceles containing a substantial amount of brain tissue can result in spasticity. The most common symptom of an anterior encephalocele is nasal obstruction, followed by CSF rhinorrhea and meningitis, with hypertelorism being less frequent.

Anterior basal encephaloceles are most commonly located at the cribriform plate (64.0%), followed by the ethmoid roof (31.3%) and sphenoid or sella (15.5%). In posterior encephaloceles, hydrocephalus is present in 40% to 60% of occipital cases, whereas frontal encephaloceles have a hydrocephalus rate of only 14%. Seizures occur in 17% of occipital encephalocele cases but are rare in anterior cases. Temporal lobe/middle cranial fossa encephaloceles may present with sudden CSF otorrhea or rhinorrhea, and repeated episodes of meningitis can occur before a diagnosis is made.

What Are the Pathological Features Of Intranasal Meningoencephalocele?

The following are the pathological features of nasal encephaloceles:

• Nasal encephaloceles involve meningeal herniation through a defect in the floor of the anterior cranial fossa, leading to an external swelling on the nose.

The following are the radiographic features of nasal encephaloceles:

• Computed Tomography Scan- CT effectively delineates bony abnormalities but is less suitable for detecting intracranial components.

• Magnetic Resonance Imaging- MRI provides better detail of soft tissue, including any intracranial connections, and reduces exposure to ionizing radiation.

How To Treat Intranasal Meningoencephalocele?

When a midline nasal swelling is present, invasive procedures or operations are deferred until an intracranial connection is excluded through CT scanning or MRI. This precaution is necessary to mitigate the risks of meningitis or cerebrospinal fluid leakage. The surgical approach for anterior encephaloceles is typically open, but an endoscopic approach can be used when the encephalocele involves the sphenoid or ethmoid region. Endoscopic endonasal surgery for anterior basal encephaloceles offers a relatively favorable risk-benefit profile with a low rate of postoperative CSF leaks.

Conclusion

Nasal encephaloceles are typically present at birth, manifesting as an external swelling on the nose. This swelling is generally soft, covered with normal skin, and enlarges with coughing or straining. Symptomatic patients often experience obstruction or rhinorrhea. Nasal encephaloceles are usually identified alongside a visible cranial bone defect. They are a type of anterior encephalocele where meningeal herniation occurs through a midline defect in the floor of the anterior cranial fossa.

Many factors influence the prognosis of an encephalocele, including its location, size, amount of brain tissue within the sac, dural sinuses in the sac, and hydrocephalus. Patients with frontoethmoidal encephaloceles generally have a better prognosis than those with occipital or parietal encephaloceles. The prognosis is also affected by the presence of additional congenital brain anomalies.