Makindo Medical Notes.com

Tends to present with paroxysms of pain which last for thirty seconds to two minutes. Often severe and debilitating.

About

• Often severe Neuropathic path in the distribution of the trigeminal nerve

Epidemiology

• Affects 1 in 10,000 each year.
• It mainly affects older people, and it usually starts in your 60s or 70s.
• Rare in younger adults. Women are more commonly affected than men

Aetiology

• 90% of cases there is microvascular compression of the Vth nerve leads to neuropathic pain is classical and is the most frequent form of TN with defined etiology.

Anatomy

• Trigeminal nerve starts at the mid-lateral surface of the pons
• Sensory ganglion (Gasserian ganglion) resides in Meckel's cave on the floor of the middle cranial fossa

Branches

• V1 superior orbital fissure (ophthalmic) - innervation passes as far back as the vertex on the scalp so theoretically pain can be felt this far back and still be trigeminal
• V2 foramen rotundum(maxillary)
• V3 foramen ovale (mandibular)

Classification

• Type 1 is purely paroxysmal and the patient is has no pain in between attacks
• Type 2 presents with persistent simultaneous, background facial pain between attacks. Type 2 is also known as atypical TN and in this type central sensitization may be responsible for the persistent pain. Neurovascular conflict may not be evident in type 2, and is found to be resistant to several treatment modalities

Clinical

• Episodic pain as can disappear for weeks to months and then recur. The pain free time often gets shorter.
• Severe lancinating electric shock like pain on one side of face < 2 minutes. There may be a lasting ache afterwards.
• Usually a single division Ophthalmic, maxillary or mandibular
• Trigger spots when touched trigger it off - shaving, talking, washing even eating, talking or even light touch
• Autonomic features such as conjunctival injection, lacrimation, nasal congestion or rhinorrhoea, eye lid oedema, ptosis, or facial sweating.
• Middle aged and after, some get depressed even suicidal as pain is so debilitating

Differential

• Multiple sclerosis - can cause a similar syndrome
• Space occupying lesion especially posterior fossa tumour s, extracranial masses along the trigeminal nerve, perineural spread of existing malignancy, cavernous sinus masses.
• Epidermoid, dermoid, or arachnoid cysts.
• Aneurysm, or arteriovenous malformation
• A tumour at the cerebellopontine angle or MS causes TN in 15% of patients

Investigations

• FBC, U&E, LFT, ESR and other bloods normal
• MRI - exclude SOL or demyelination and can show the neurovascular compression of the nerve

Management

• Medical : Carbamazepine is considered the first-line medication for the initial medical treatment of trigeminal neuralgia symptoms. Carbamazepine 100 mg BD PO, and titrate in steps of 100 - 200 mg every two weeks, until pain is relieved. For most 200 mg TDS or QDS suffices. However can go to 400 mg QDS. If fails to work then seek specialist review.
• Others are, Sodium Valproate 400 mg BD which can be increased, Phenytoin, Clonazepam
• Baclofen 10 mg TDS which can be up titrated used particularly in those with MS and trigeminal neuralgia.
• Neurosurgical Referral to assess for treatment: 80-90% are caused by vascular compression and can be treated surgically with Microvascular decompression or Ablative procedures, such as radiofrequency rhizotomy and gamma knife, that lesion the trigeminal nerve

References

• Trigeminal neuralgia. New classification and diagnostic grading for practice and research
• Trigeminal Neuralgia BMJ Group