IMAGING RECOMMENDATION FOR SKULL BASE AND TEMPORAL BONE TUMORS
The skull base is a complex osseous structure that serves as a conduit
between the intracranial and extracranial compartments. It contains
several neural foramina and fissures with traversing neurovascular
structures 20. As in
adults, there is a wide variety of benign and malignant skull base
tumors that may occur in the pediatric population such as nerve sheath
tumors, glomus tumors, RMS, Ewing sarcoma, olfactory
neuroblastoma/esthesioneuroblastoma, chondrosarcoma and chordoma21-23. Systemic
malignancies such as lymphoma, leukemia and especially LCH may involve
the skull base.
Clinical presentation of children with skull base tumors varies with
sub-location: anterior, middle versus posterior skull base. Children
with anterior skull base mass lesions often present late and without
distinction between neoplastic and non-neoplastic entities or between
benign and malignant neoplasms. Nasal obstruction especially long term
unilateral nasal obstruction, sinonasal pain, epistaxis, excessive
lacrimation, anosmia and even visual changes may be presenting symptoms24. Tumors of the
middle skull base may present with headache, hypothalamic-pituitary
dysfunction, visual changes, facial dysesthesia and pain, deficits of CN
III-XI, facial deformity and oropharyngeal obstruction. Finally, tumors
of the posterior skull base present with headache, neck pain which may
be from craniocervical instability, torticollis secondary to the
craniocervical junction involvement, or cranial nerve dysfunction
including visual abnormalities and dysphagia with involvement of the
hypoglossal canal and jugular foramen25.
Temporal bone neoplasms in the pediatric population are exceedingly
rare. These typically include RMS. Other sarcomas are rare. Systemic
malignancies such as lymphoma, leukemia and especially LCH may involve
the temporal bone. Patients typically present with signs and symptoms
that mimic refractory and severe ear infection. Additionally, common
presenting symptoms include hearing loss, otorrhea, otalgia, vertigo and
headache. Facial weakness and diplopia may also occur. Extension of the
mass to involve the orbital apex, cavernous sinus, hypoglossal canal and
jugular foramina may produce additional cranial nerve dysfunction
symptoms. Finally, with invasion of the dura, patients may present with
CSF leakage and/or meningitis26.
Imaging in Skull Base and
Temporal Bone Tumor Staging
Both CT and MRI play complementary roles for evaluation of skull base
and temporal bone tumors at both diagnosis and follow up27,28.
Similar to head and neck tumors in other subsites, goals of imaging are
to evaluate the origin and the extent of the lesion as well as to
differentiate between neoplastic and non-neoplastic entities or between
benign and malignant neoplasms. Following initial diagnosis, staging
evaluation typically occurs via the AJCC TNM classification system for
select sites. Esthesioneuroblastoma staging may occur via the Kadish or
modified Kadish staging or Dulgerov systems which require imaging
assessment of regional tumor invasion such as paranasal sinuses, orbits,
skull base, dural and brain involvement, as well as evaluation of
co-existing nodal and distant metastases29. Note that a
universally agreed upon staging system does not exist for temporal bone
tumors other than RMS.
Staging of skull base and temporal bone RMS, like all other RMS in the
head and neck, is via the IRSG staging system9.
Staging of skull base and temporal bone RMS is recommended via the IRSG
staging system. (GRADE A, SOR 1.08, very strong recommendation)