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Congenital Midline Masses

Background

  • Incidence is 1:20,000 to 1:40,000

  • Includes nasal dermoid, glioma, and encephalocele

Embryology

  • Formation due to failure of closure of the anterior neuropore

  • Transient opening between frontal and nasal bones known as fonticulus frontalis at eighth week of gestation

    1. Prenasal space forms between frontal and nasal bones and the cartilaginous nasal capsule.

    2. Foramen cecum, an opening between the skull base and frontal bone, into the prenasal space. A projection of dura (diverticulum) passes through this foramen.

    3. Dural diverticulum typically regresses with fusion of skull base and frontal bone. Failure results in neuroglial or ectodermal elements to remain in prenasal space with potential intracranial connection.

Nasal Dermoid

  • Pathophysiology

    1. Retained ectodermal and mesodermal elements from incomplete regression of dura from prenasal space or fonticulus frontalis. Form cysts filled with squamous epithelium, keratin debris, and connective tissue

  • Epidemiology

    1. Most common midline nasal mass

    2. 1% to 3% of all dermoid cysts, 11% to 12% of head and neck dermoids

  • Presentation

    1. Most commonly on nasal dorsum, may occur from nasal tip to glabella

    2. Can be intranasal, intracranial, or extranasal masses

    3. Nasal pit present in 45% to 84%, may contain hair

    4. Firm, nontender, nonpulsatile, noncompressible mass without transillumination

    5. Tendency for repeated infections, ranging from cellulitis to abscess

  • Diagnosis

    1. CT and/or MRI, important to determine intracranial extension

  • Complications

    1. Repeat infection, nasal skin necrosis, cartilage and bony destruction, CSF leak, meningitis

  • Treatment

    1. Early excision with removal of cyst, tract and involved bone, cartilage, and septum

    2. Open rhinoplasty approach optimal with wide exposure and superior cosmesis

Nasal Glioma

  • Pathophysiology

    1. Unencapsulated, ectopic glial tissue

    2. Mass covered with nasal mucosa or skin containing heterotopic glial cells

  • Presentation

    1. 20% with intracranial connection through stalk

    2. 60% external, 30% internal, 10% combined

    3. Firm, nontender, nonpulsatile, noncompressible mass without transillumination

    4. External are typically red with telangiectasias, internal glistening gray or purple

  • Diagnosis

    1. CT and/or MRI

  • Complications

    1. Cosmetic deformity, nasal obstruction, meningitis

  • Treatment

    1. Complete surgical excision

    2. External nasal approach or lateral rhinotomy for extracranial lesions

    3. Intracranial extension may warrant craniotomy to anterior cranial fossa

Encephalocele

  • Pathophysiology

    1. Herniation of CNS tissue through defect at the skull base, meningeal sac containing glial tissue

      • Failed closure of anterior neuropore or poor migration of neural crest cells, communicates with the subarachnoid space

    2. Terminology differ based on CNS contents

      • Meningocele (meninges only)

      • Meningoencephalocele (meninges and brain)

      • Meningoencephalocystocele (meninges, brain, and ventricular system)

    3. Varies by location

      • Posterior most common (occipital, nonnasal type)

      • Anterior

        • – Sincipital (frontoethmoid): defect at foramen cecum between frontal and ethmoid bones

          • Nasofrontal—glabellar

          • Nasoethmoid—lateral nose

          • Nasoorbital—medial orbital wall

        • – Basal

          • Transethmoidal

          • Sphenoethmoidal

          • Transphenoidal

          • Sphenomaxillary

  • Epidemiology

    1. 1:4000 live births

  • Presentation

    1. External lesions are soft, compressible masses

    2. Intranasal lesions are bluish, high in nasal cavity, compressible, and pulsatile

  • Diagnosis

    1. CT and/or MRI (look for bony defects and intracranial communication)

    2. Positive Furstenberg sign (expansion of mass with crying or ...

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