What are the common diseases of the Trigeminal nerve in adults, particularly those over 50 years old?

Common Diseases of the Trigeminal Nerve in Adults Over 50

Trigeminal neuralgia is the most common and clinically significant disease affecting the trigeminal nerve in adults over 50, with incidence increasing with age and average onset between 50-60 years. 1

Primary Trigeminal Nerve Disorders

Trigeminal Neuralgia (Classical)

• Classical trigeminal neuralgia is caused by neurovascular compression at the trigeminal root entry zone near the brainstem, leading to focal demyelination and ectopic impulse generation 2
• Presents as sudden, severe, brief, stabbing "electric shock-like" pain attacks lasting seconds to minutes in one or more trigeminal nerve divisions (V1, V2, or V3) 3, 1
• Mandatory refractory periods occur between attacks—the inability to trigger attacks repeatedly without pain-free intervals should prompt consideration of alternative diagnoses 4
• Triggered by non-noxious stimuli such as talking, eating, washing the face, brushing teeth, shaving, light touch, or even a cool breeze 3, 1
• MRI demonstrates neurovascular compression with 83-100% congruence with surgical findings 4

Type 2 Trigeminal Neuralgia

• Characterized by prolonged continuous background pain between the characteristic sharp shooting attacks 4
• May originate from more central mechanisms rather than peripheral neurovascular compression 4
• Associated with worse treatment outcomes compared to classical presentation 3

Trigeminal Neuropathy

• Must be distinguished from trigeminal neuralgia—presents with sensory deficits in the trigeminal distribution between pain episodes, unlike classical trigeminal neuralgia which has normal examination findings between attacks 2
• Sensory abnormalities include facial numbness or altered sensation 5
• Requires urgent imaging to rule out secondary causes including tumors, inflammatory conditions, or structural lesions 4

Secondary Causes Affecting the Trigeminal Nerve

Multiple Sclerosis

• Produces trigeminal neuralgia through brainstem demyelinating plaques affecting the trigeminal nerve nuclei or pathways 2
• Requires brainstem imaging to identify demyelinating lesions 2
• More common in younger patients but can present in adults over 50 5

Structural Lesions

• Tumors can affect the trigeminal nerve anywhere along its course from brainstem to peripheral branches 5, 2
• Perineural spread of malignancies should be considered in the differential diagnosis 6
• Vascular lesions including compressing vascular loops, aneurysms, and vertebrobasilar dolichoectasia 5

Post-Herpetic Neuralgia

• Develops following herpes zoster infection in the trigeminal distribution 2
• Presents as continuous burning pain at the site of previous herpes zoster eruption with allodynia and hyperalgesia 4
• Distinct from classical trigeminal neuralgia by its continuous rather than paroxysmal nature 4

Post-Traumatic Trigeminal Neuropathy

• Develops within 3-6 months following dental procedures, facial trauma, or surgical interventions 4, 2
• Characterized by continuous burning, tingling pain rather than paroxysmal attacks 4

Motor Manifestations

• Weakness or paralysis of mastication muscles can occur when the mandibular division (V3) is affected 5
• Motor abnormalities manifest as weakness when chewing food 5

Critical Diagnostic Approach

Imaging Requirements

• MRI with contrast is the gold standard and mandatory for all suspected trigeminal nerve disorders 5, 6, 2
• High-resolution thin-cut sequences through the entire trigeminal nerve course from brainstem to peripheral branches are essential 2
• 3D heavily T2-weighted sequences combined with MR angiography characterize neurovascular compression 2
• CT remains useful for evaluating skull base bony anatomy and neural foramina 5

Key Clinical Distinctions

• Paroxysmal sharp pain with refractory periods = classical trigeminal neuralgia from peripheral nerve pathology 4
• Continuous burning pain = post-traumatic neuropathy, post-herpetic neuralgia, or atypical odontalgia 4
• Sharp pain with autonomic features (tearing, conjunctival injection, rhinorrhea) = trigeminal autonomic cephalgias (SUNCT/SUNA), not true trigeminal neuralgia 4

Common Pitfalls to Avoid

• Do not diagnose trigeminal neuralgia if continuous pain is present without the characteristic paroxysmal attacks and refractory periods 4
• Do not skip MRI imaging—it is essential to distinguish classical from secondary causes and guide treatment decisions 2, 1
• In patients over 50 with eye pain and swelling, consider giant cell arteritis in addition to trigeminal disorders 6, 4
• Trigeminal neuralgia does not typically cause visible inflammation or swelling—if present, consider alternative diagnoses 4