<aside>

Intraconal orbital lesions are pathologies located within the muscle cone of the orbit, i.e. inside the boundaries formed by the extraocular rectus muscles and their intermuscular septa. They represent an important group of orbital lesions, distinct from extraconal (outside the cone) and conal lesions.

</aside>

Anatomy

<aside>

Lesions here often cause axial proptosis (forward displacement of the globe along its long axis), in contrast to extraconal lesions which tend to produce eccentric/oblique proptosis.

</aside>

Muscle cone: Formed by the rectus muscles (superior, inferior, medial, lateral).
Contents of intraconal space:
- Optic nerve and its sheath.
- Ophthalmic artery and ciliary vessels.
- Ciliary ganglion.
- Fat and small veins.

Etiopathology

Intraconal lesions can be classified as follows:

Type	Etiology
Vascular	• Cavernous hemangioma (most common benign intraconal mass in adults).
• Venous varix.
• Lymphangioma.
• Hemangiopericytoma.
Neurogenic	• Optic nerve sheath meningioma.
• Optic nerve glioma.
• Schwannoma (from ciliary nerves).
• Neurofibroma.
Neoplastic	• Lymphoma.
• Metastasis (breast, lung, melanoma).
• Rhabdomyosarcoma (children).
Inflammatory	• Idiopathic orbital inflammatory syndrome (orbital pseudotumor).
• Sarcoidosis.
• Granulomatosis with polyangiitis.
Other rare lesions	• Dermoid/epidermoid cysts (usually extraconal, but may extend intraconally).
• Orbital hydatid cyst (endemic areas).

Clinical Presentation

Axial proptosis (hallmark).
Diplopia (extraocular muscle involvement).
Vision loss (optic nerve compression).
Pain (inflammatory/infective vs painless in vascular/neoplastic).

Radiology

<aside>

General signs: Intraconal lesions usually cause axial proptosis, optic nerve displacement, and alteration of orbital fat planes.

</aside>

Modality	Imaging features
Cavernous hemangioma	• Well-defined, intraconal, usually lateral to optic nerve.
• CT: Homogeneous, isodense; MRI: Iso- to hypointense on T1, hyperintense on T2.
• Shows progressive, centripetal contrast filling on dynamic imaging (classic sign).
Optic nerve glioma	• Fusiform enlargement of optic nerve, seen in children, NF-1 association.
• MRI: T2 hyperintense, variable enhancement.
Optic nerve sheath meningioma	• Middle-aged females.
• CT/MRI: “Tram-track” sign (enhancing sheath surrounding a non-enhancing optic nerve).
• May show calcifications.
Venous varix	• Lesion enlarges with Valsalva or prone positioning.
• MRI/CT: Dilated venous channel; phleboliths possible.
Lymphoma	• Well-defined, mold around orbital structures without bone destruction.
• Homogeneous soft-tissue attenuation; iso- to hypointense on T1, hypointense on T2; mild enhancement.
Orbital pseudotumor	• Ill-defined, painful, rapid onset.
• Involves both intraconal and extraconal spaces.
• MRI: T2 hypointense, shows intense enhancement; response to steroids is characteristic.
Metastasis	• Often breast, lung, melanoma.
• Variable imaging, but often enhancing intraconal soft tissue mass.