JNA on CT Scan: Complete Exam Guide

Part 1: How to Start Presenting the CT Scan (Step-by-Step Script)

Step 1 - Identify the type of scan

"This is a CT scan of the paranasal sinuses and nasopharynx, presented in [axial/coronal] cuts, [with/without] contrast enhancement."

• Bone window vs soft tissue window matters. JNA is best appreciated on both.
• If contrast is given: soft tissue window will show intense homogeneous enhancement - this is a key finding.

Step 2 - Describe the mass

"There is a well-defined soft tissue mass in the nasopharynx and [right/left] nasal cavity..."

• Location - nasopharynx, posterior nasal cavity, extending into pterygopalatine fossa (PPF)
• Side - unilateral (almost always)
• Density - soft tissue density on plain CT
• Enhancement - intense, homogeneous enhancement post-contrast (highly vascular)
• Borders - well-defined, lobulated

Step 3 - The Pathognomonic Finding (Say this confidently)

"There is widening of the pterygopalatine fossa on the [right/left] side, with anterior bowing of the posterior wall of the maxillary sinus - this is pathognomonic for juvenile nasopharyngeal angiofibroma."

Step 4 - Describe bony changes

• Erosion of the base of the medial pterygoid plate (early and consistent finding)
• Erosion/widening of the sphenopalatine foramen (site of origin)
• Erosion of the vidian canal (look for this specifically - important)
• Anterior bowing of the posterior wall of the maxillary sinus ("Holman-Miller sign" or "antral sign")
• Any erosion of the skull base, pterygoid plates, or orbital walls (advanced disease)

Step 5 - Extent of disease (Staging)

"The mass appears to extend into the [pterygopalatine fossa / infratemporal fossa / sphenoid sinus / orbit / intracranially]..."

Step 6 - Your Diagnosis

"In view of a unilateral nasopharyngeal mass in a young male with widening of the pterygopalatine fossa, anterior bowing of the posterior wall of the maxillary sinus, erosion of the medial pterygoid plate and sphenopalatine foramen, the most likely diagnosis is Juvenile Nasopharyngeal Angiofibroma (JNA)."

Part 2: The CT Image You Will See

Part 3: Classic CT Signs - Memorize These

Part 4: Full Clinical Profile (What the Examiner Expects You to Know)

Definition

Epidemiology

• Almost exclusively in adolescent males (ages 10-25 years)
• Accounts for only 0.05% of all head and neck tumors but is the most common benign nasopharyngeal tumor
• No reliable racial predilection, but higher reported incidence in India and Egypt

Origin

• Arises at the sphenopalatine foramen / base of the pterygoid process (where the pterygoid process meets the body of the sphenoid)
• Primary epicenter: pterygopalatine fossa (PPF)

Pathology

• Histology: Vascular spaces (endothelium-lined, NO smooth muscle layer) embedded in a fibrous stroma
• The vessels lack a muscular coat, which is why they cannot contract - hence the profuse, uncontrollable bleeding
• The stroma contains stellate fibroblasts and collagen
• Considered by many to be a vascular malformation/hamartoma rather than a true neoplasm
• Androgen-dependent tumor - explains why it occurs in pubescent males and may involute after puberty

Clinical Features

• Nasal obstruction - unilateral, progressive (most common early symptom)
• Epistaxis - recurrent, profuse, often intractable (hallmark symptom)
• Advanced cases: cheek swelling (ITF), proptosis/diplopia (orbital), headache (intracranial)
• Endoscopy: smooth, hypervascularized, reddish-purple mass behind the middle turbinate, laterally displacing it

Part 5: Staging Systems (Examiner Favorite)

Radkowski Staging (Most Commonly Used in Exams)

Andrews-Fisch Staging (Also Common)

Exam tip: Know Radkowski well - it's the one most examiners quiz. Mention that the pterygopalatine fossa is the key landmark between Stage I and Stage II.

Part 6: Imaging - What Each Modality Shows

CT (What you're being tested on)

• Gold standard for bone detail - shows erosion of pterygoid plates, skull base, vidian canal
• Post-contrast: intense homogeneous enhancement
• Shows: tumor extent, PPF widening, Holman-Miller sign, sinus involvement
• Limitation: poor soft tissue differentiation from retained secretions vs. tumor

MRI

• Best for soft tissue extent - differentiates tumor from retained secretions in sinuses
• T1: intermediate signal with flow voids (characteristic of high vascularity)
• T2: heterogeneous with flow voids
• T1 post-contrast: intense enhancement
• Best for orbital, intracranial, and cavernous sinus involvement
• Flow voids on both T1 and T2 = salt-and-pepper appearance (characteristic)
• MRI is preferred for staging intracranial extension

Plain X-ray (PNS views)

• Waters' view: soft tissue mass in nasopharynx, anterior bowing of posterior maxillary sinus wall
• Rarely used today but may be asked about

Digital Subtraction Angiography (DSA)

• Shows the vascular supply in detail
• Blood supply: primarily internal maxillary artery (branch of ECA) and ascending pharyngeal artery
• Advanced lesions: ICA supply (up to 35% of cases)
• DSA is done prior to embolization, not primarily for diagnosis

Part 7: Differential Diagnosis of Unilateral Nasal Mass (Examiner Will Ask)

Part 8: Treatment (Examiner Will Definitely Ask)

Preoperative Embolization (Standard of Care)

• Done 24-48 hours before surgery using polyvinyl alcohol (PVA) particles
• Dramatically reduces intraoperative hemorrhage
• DSA first - maps vasculature, identifies ICA feeders
• If ICA feeders present: direct tumor puncture with liquid embolic agents (Onyx/NBCA) may be used

Surgery - Primary Treatment

• Endoscopic resection - now standard for Stage I, II, and selected Stage III
• Open approaches for advanced lesions:
  • Transpalatal approach (Stage I/II)
  • Lateral rhinotomy / midfacial degloving (Stage II/III)
  • Infratemporal fossa approach (Stage III with ITF extension)
  • Combined craniofacial (Stage IV/intracranial)

Radiotherapy

• Reserved for surgically inaccessible lesions (cavernous sinus, intracranial)
• Also used for recurrences not amenable to surgery
• Risk: radiation-induced malignancy in young patients

Hormonal therapy

• Anti-androgens (flutamide) - limited historical use, not standard

Observation

• Residual disease after surgery may be monitored with serial MRI if in a pubescent patient, as spontaneous involution is possible

Recurrence

• Rate: 6-24%, higher in advanced stages
• Monitor with MRI
• Re-embolization and re-surgery is the standard approach

Part 9: Likely Examiner Questions and How to Answer

Widening of the pterygopalatine fossa with anterior bowing of the posterior wall of the maxillary sinus (Holman-Miller sign/antral sign).

It is androgen-dependent. Androgen receptors are expressed in the fibrous stroma, and testosterone stimulation at puberty is thought to drive its development. It may involute spontaneously after puberty.

The vascular spaces in JNA lack a smooth muscle layer and cannot contract. Biopsy causes profuse, uncontrollable hemorrhage. Diagnosis is made on clinical + imaging grounds.

The sphenopalatine foramen / base of the pterygoid process (junction of the pterygoid process and the body of the sphenoid). The pterygopalatine fossa is always the primary epicenter.

Primarily from the internal maxillary artery (branch of external carotid artery) and ascending pharyngeal artery. In advanced lesions, the internal carotid artery also contributes (found in up to 35% of cases). This is important before embolization.

Signal voids on T1 and T2 weighted sequences due to rapid blood flow through large intralesional vascular channels. This gives the "salt-and-pepper" or "honeycomb" appearance on MRI and confirms high vascularity.

Anterior bowing of the posterior wall of the maxillary sinus on CT or plain X-ray (Waters' view), caused by the expanding JNA mass pressing forward from the pterygopalatine fossa. It is pathognomonic of JNA.

JNA: young male, PPF widening, intense contrast enhancement, Holman-Miller sign, no calcification. Inverted papilloma: older male, arises from lateral nasal wall/middle meatus, may have calcifications, thickened (sclerotic) bony margins, less intense enhancement.

Performed 24-48 hours before surgery using PVA particles via DSA. Reduces intraoperative blood loss dramatically, improves visibility of tumor margins, and makes complete resection easier. It does NOT improve long-term recurrence rates.

Endoscopic endonasal resection. It is now the standard approach for Stage I, II, and even selected Stage III lesions, replacing older open approaches.

Rarely. Malignant transformation to fibrosarcoma or angiofibrosarcoma has been rarely reported, usually following radiotherapy. The lesion is otherwise histologically benign.

Part 10: The Perfect Examiner Script (Put It Together)

"This is a contrast-enhanced CT of the paranasal sinuses and skull base in the [axial/coronal] plane. I can see a well-defined, lobulated soft tissue mass in the posterior nasal cavity and nasopharynx on the right side, showing intense post-contrast enhancement, consistent with a highly vascular lesion.

The key findings are: widening of the right pterygopalatine fossa, erosion of the base of the medial pterygoid plate, erosion of the sphenopalatine foramen, and anterior bowing of the posterior wall of the right maxillary sinus - which is the Holman-Miller sign.

The mass appears to extend into the right pterygopalatine fossa and there is [describe extent]. There is no evidence of intracranial extension / orbital involvement [or state what is present].

Based on these findings - a unilateral, highly enhancing nasopharyngeal mass with pathognomonic pterygopalatine fossa widening and the antral sign in what appears to be a young male patient - the most likely diagnosis is Juvenile Nasopharyngeal Angiofibroma, Radkowski Stage [IIb, for example].

I would recommend complementary MRI with contrast for precise soft tissue staging, and digital subtraction angiography prior to preoperative embolization and surgical resection."