Orbital apex syndrome

Characterized by vision loss from optic neuropathy and ophthalmoplegia due to the involvement of ocular motor nerves in the anatomical region of the orbital apex.

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Anatomy

Structure	Contents
Superior orbital fissure	CN III, CN IV, CN V1, CN VI, superior ophthalmic vein
Inferior orbital fissure	CN II
Optic canal	CN II, ophthalmic artery
Cavernous sinus	CN III, CN IV, CN V1, CN V2, CN VIa, cavernous portion of ICAa

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Aetiology

Inflammatory causes:

• Sarcoidosis
• ANCA (Anti-neutrophil cytoplasmic antibody) associated vasculitides:
  1. Granulomatosis with polyangiitis (known earlier as Wegener’s Granulomatosis)
  2. Microscopic polyangiitis
  3. Churg- Strauss syndrome
• Tolosa Hunt syndrome (THS)
• IgG4-RD (Immunoglobulin G4- Related Disease)
• IgG4-ROD (Immunoglobulin G4- Related Orbital Disease)

Infectious causes:

Can be caused by viral, bacterial, fungal and parasitic infections which result from contiguous infections of the paranasal sinuses or other surrounding structures.

• Bacterial: Staphylococcal species, Streptococcus pneumoniae, and gram-negative bacilli like Pseudomonas aeruginosa, Klebsiella and Proteus species
• Fungal: Aspergillus and Mucor
• Viral: Herpes zoster ophthalmicus (rare complication)
• Parasitic: Cysticercosis

Neoplastic causes:

• Head and neck tumors
• Hematologic cancers
• Metastatic lesions

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Pathophysiology

Orbital Apex syndrome constitutes a syndrome characterized by involvement of the following cranial nerves:

• Optic nerve (II C.N)
• Oculomotor nerve (III C.N)
• Trochlear nerve (IV C.N)
• Abducens nerve (VI C.N)
• The first division of the trigeminal nerve (ophthalmic division of V C.N)

Trauma and Iatrogenic causes:

• Cranio-maxillo-facial trauma
• Surgeries of the orbit and sinuses

Vascular causes:

• Carotid cavernous fistulas (CCF)
• Carotid cavernous aneurysms
• Cavernous sinus thrombosis (CST)

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Clinical features

Common presentation:

• Vision loss
• Painful and limited eye movements

Other features:

• Proptosis
• Choroidal folds

Lesion localizing symptoms:

• Pain around the orbit or the skin around the orbit (CN V₁)
• Facial pain (CN V₂)
• Presence/absence of corneal sensations and corneal reflex (CN V₁)
• Relative Afferent Pupillary Defect (RAPD) (CN II)
• Anisocoria (side of dilated pupil indicating the involvement of the pupillary fibers of CN III)
• Optic disc edema or optic atrophy (CN II)
• Ophthalmoplegia (CN III, IV, VI nerves in any combination)
  • Can present with vertical, horizontal or torsional diplopia with or without compensatory abnormal head postures.

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Diagnosis

Clinical evaluation holds key to diagnosis which is aided then by certain serological and lab investigations and neuro-imaging modalities including brain and orbital MRI (Magnetic Resonance Imaging) with contrast, CT (Computed Tomography) scans.

Relative afferent pupillary defect (RAPD):

Direct pupillary light reaction and the accompanying consensual reaction of the opposite pupil are weaker on illumination of the affected eye than on illumination of the unaffected eye due to unilateral or asymmetrical disease of the retina or optic nerve

Brain and orbit MRI:

Imaging modality of choice and should be performed with gadolinium in case of suspected inflammatory conditions

• Soft tissue involvement
• Cavernous sinus and intracranial extension
• Bone marrow involvement
• Perineural spread of tumors

Differential diagnosis:

Due to anatomical proximity, these syndromes can have overlapping features

• Superior orbital fissure syndrome “Rochon -Duvigneaud syndrome”: Characterized by multiple cranial nerve involvement but generally spares the optic nerve
• Cavernous sinus syndrome: Orbital apex syndrome + involvement of the sympathetic fibers and the maxillary division of the trigeminal nerve
  • Main differentiator is the optic nerve involvement in orbital apex syndrome

Condition	Cranial Nerves Involved	Cranial Nerves Not Involved
Orbital apex syndrome	II, III, IV, V1 ± V2
Superior orbital fissure syndrome	III, IV, V1 ± V2	II
Cavernous sinus syndrome	III, IV, V1	II, V2