The Pediatric Central Skull Base

Gary L. Hedlund, D.O.Primary Children’s Medical Center

Salt Lake City, Utah

Pre-SO 1

Pre-SO 2

Inter-S S

Post-SO

SOS

BO-O

CPC

Ali-SO

Orb-S O

Central Skull Base Ossification Centers

Presphenoidal ossification center 1 → sphenoid sinusPresphenoidal ossification center 2 → sphenoid sinusIntersphenoidal synchondrosis → Closes, 3mo; if no, P-CPCPostsphenoidal ossification center → basisphenoidSphenooccipital synchondrosis → Closes by age 25 yearsBasioccipital ossification center → basiocciputOrbitosphenoidal ossification center → LWSAlisphenoidal ossification center → GWSCraniopharyngeal canal → Dermoid, epidermoid, lipoma, cephalocele

The Chondrocranium

• Portion of the neocranium formed by endochondral ossification

• 25 centers of ossification

• 18 sutures and/or synchondroses

• Anatomic variants and developmental anomalies abound

Central Skull Base

Jinkins JR . Atlas of Neuroradiologic Embryology, Anatomy, and Variants. 2000: LW&W

Newborn Central Skull Base

Newborn

Sphenooccipital Synchondrosis

NB

3 yrs

5 yrs

Sphenooccipital Synchondrosis

10 yrs

14 yrs

18-year-old female with closed head trauma

Neonatal Central Skull Base

Newborn6 Mo

Craniopharyngeal Canal

5 yrs

Craniopharyngeal Canal

Larsen WJ. Human Embryology, 2ND ed. Saunders; 1997

Craniopharyngeal Canal

Courtesy Bronwyn E. Hamilton, MD

Infant Central Skull Base

Age Related T1WI Marrow Changes

Newborn

3 yrs

7 yrs

Sphenoid Bone Pneumatization

• Follows marrow conversion

• Begins at about 1 – 2 years

• Reaches the sella by about 7 years

• Mature by 15 years

• Asymmetric pneumatization is common

• Lateral recess pneumatization– Splays distance between f. rotundum & vidian canal

11-year-old boy with headache and lethargy

Leukemic marrow infiltration - ALL

Three-year-old with nasal congestion

Diagnostic Considerations?

1. Metastasis

2. Rhabdomyosarcoma

3. LCH

4. Chordoma

5. Chondrosarcoma

Langerhans’ Cell Histiocytosis

• Denditic cell proliferation

• Skull (calvarium>orbit>skullbase)– Mandible> ribs> femur> pelvis> spine

• Imaging– Punched-out, beveled, lack of sclerosis – Sequestration +/-– T1 hyper - isointensity ~ lipid laiden histiocytes– T2 signal variable

Metastatic Disease

• Leukemia

• Neuroblastoma

• Sarcomas– Rhabdomyosarcoma

– Soft part sarcoma

– Clear cell sarcoma

Seven-year-old female with headache and nasal congestion

Rhabdomyosarcoma• Most common childhood soft tissue sarcoma• More common in African American children • H&N involvement in 50%

– Orbit– Parameningeal

• Nasal cavity, NP, sinuses, parapharyngeal, masticator, pterygopalatine fossa, middle ear

– Other • Cervical nonparameningeal

Imaging of Rhabdomyosarcoma

• CT– Bony lysis – ST attenuation

• MR

T1 hypo to isointense

T2 hyperintense

Variable enhancement

NonrhabdomyosarcomaSoft Tissue Sarcomas (NRSTSs)

• Fibrosarcoma

• Primitive neuroectodermal tumor (PNET)

• Malignant peripheral nerve sheath tumor

• Ewing sarcoma

• Synovial sarcoma

Six-year-old male with chronic headaches

Clival Chordoma

• Primitive notocord remnant

• Location– 35% skull base– 50% sacrococcygeal– 15% vertebral body

Clival Chordoma

• T1WI– Intermediate to low

signal– Focal hemorrhage

• T2WI– High signal intensity– Heterogeneous

• T1 C+– Honeycomb

enhancement

Hemorrhage ~ 30%

Chordoma and TSC

• TSC is a harmatoneoplastic syndrome

• Autosomal dominant trait

• Nonsense mutations in TSC1 (9q34)– Found in:

• Symptomatic father • Clival chordoma of the son

Borgel J et al. Eur J Pediatr (2001) 160:138

Fourteen-year-old female with frontal headaches

Kapoor V et al AJNR 23: 476-479, March 2002

Neurenteric Cyst

Paraclival Neurenteric Cyst

• Dysgenesis of notocord & neurenteric canal. Similar to Rathke cleft and colloid cysts

• Most involve – Craniovertebral junction and posterior fossa

• Histopathiology– Type A, resemble respiratory or GI epithelium– Type B, smooth muscle, glandular, and lymphoid– Type C, like Type B + glial elements

Summary

• Review age related ossification and maturation

• Identify anatomic variants

• Review anomalies of development

• Highlight pseudolesions and tumefactions of the central skull base

Thank you

gary.hedlund@imail.org