How do you differentiate and treat paroxysmal hemicrania (PH) versus trigeminal neuralgia (TN)?

Differentiating and Treating Paroxysmal Hemicrania vs Trigeminal Neuralgia

Paroxysmal hemicrania (PH) and trigeminal neuralgia (TN) are distinguished primarily by attack duration, frequency, autonomic features, and response to indomethacin—PH has shorter attacks (2-30 minutes) occurring more frequently (>5 daily) with prominent cranial autonomic symptoms and absolute response to indomethacin, while TN has very brief attacks (seconds to 2 minutes) with trigger factors, no autonomic features, and responds to anticonvulsants. 1

Key Clinical Differentiators

Attack Characteristics

Duration:

• TN: Paroxysmal attacks lasting 2 seconds to 2 minutes with a refractory period between attacks 1
• PH: Attacks lasting 2-30 minutes (mean <20 minutes) without refractory periods 2

Frequency:

• TN: Multiple attacks throughout the day but with refractory periods between episodes 1
• PH: Multiple daily paroxysms (>5 per day, up to 40 daily) occurring without refractory periods 2

Pain Quality:

• TN: Sharp, shooting, electric shock-like pain that is frightful in nature 1
• PH: Severe unilateral headache in ophthalmic division distribution, often described as throbbing or stabbing 2

Anatomical Distribution

TN:

• Unilateral pain following trigeminal nerve distribution, most commonly second (maxillary) and third (mandibular) divisions 1
• Extraoral and intraoral locations 1

PH:

• Side-locked unilateral headache in the distribution of ophthalmic division of trigeminal nerve 2
• Orbital, supraorbital, and temporal regions 2

Autonomic Features

TN:

• No cranial autonomic symptoms 1
• May have light touch-evoked pain, rarely sensory changes 1

PH:

• Profound ipsilateral cranial autonomic symptoms are mandatory: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, eyelid edema, facial sweating, miosis/ptosis 2
• Restlessness during attacks (recently added to ICHD criteria) 2

Trigger Factors

TN:

• Light touch, washing, cold wind, eating, brushing teeth are classic triggers 1
• Trigger zones are characteristic 1

PH:

• Attacks are mostly spontaneous 2
• No typical mechanical trigger zones 2

Diagnostic Workup

Clinical Diagnosis

For TN:

• Diagnosis is made almost entirely on clinical history focusing on paroxysmal attacks, trigger factors, pain distribution, and refractory periods 3
• Examine for light touch-evoked pain in affected trigeminal distribution 3
• Document any sensory changes (rare but important) 3

For PH:

• Clinical diagnosis requires multiple daily attacks with cranial autonomic symptoms 2
• Absolute response to therapeutic doses of indomethacin is mandatory for diagnosis 2

Imaging Protocol

Both conditions require MRI to exclude secondary causes:

• High-resolution MRI with contrast of the trigeminal ganglion including 3D heavily T2-weighted sequences, MRA, pre- and post-contrast imaging, and thin-cut high-resolution techniques through the entire trigeminal nerve course 1, 4, 5
• For TN: MRI identifies neurovascular compression (most common cause in classical TN) and excludes multiple sclerosis, tumors, or other structural lesions 1, 4
• For PH: MRI excludes secondary causes and may reveal hypothalamic involvement in functional imaging studies 2
• CT is complementary for evaluating osseous skull base integrity 1

Important Diagnostic Pitfalls

Watch for PH-tic syndrome:

• Rare coexistence of both conditions in the same patient, occurring either synchronously or separately 6, 7, 8
• Each component responds to its respective treatment (indomethacin for PH, anticonvulsants for TN) 7, 8
• Can present as clinically isolated syndrome of CNS with demyelinating lesions 6

Differential diagnoses to exclude:

• SUNCT/SUNA: Rapid attacks lasting seconds to several minutes (up to 200 daily), no refractory period, prominent autonomic features, responds to lamotrigine 1
• Cluster headache: Longer duration attacks (15-180 minutes), less frequent, different treatment response 2
• Giant cell arteritis in patients >50 years: Check ESR and CRP immediately to prevent blindness 3

Treatment Algorithms

Trigeminal Neuralgia Treatment

First-line pharmacological management:

• Carbamazepine: Start 200 mg twice daily, increase by 200 mg weekly as needed, maximum 1200 mg/day 3
• Oxcarbazepine: Equally effective alternative with fewer side effects 3

Second-line/add-on therapy:

• Lamotrigine, baclofen, gabapentin, or pregabalin 3

Surgical intervention:

• Obtain neurosurgical consultation early when medical management fails or side effects become intolerable 3
• Microvascular decompression: Only non-ablative procedure and first-line surgery for patients with documented neurovascular compression on MRI 3
• Other options include percutaneous procedures and radiosurgery 9

Paroxysmal Hemicrania Treatment

First-line treatment:

• Indomethacin: Absolute response required for diagnosis; therapeutic doses typically 75-225 mg daily 2
• Complete pain relief confirms diagnosis 2

Alternative treatments for indomethacin-intolerant patients:

• Other COX-2 inhibitors 2
• Topiramate 2
• Calcium-channel blockers 2
• Epicranial nerve blocks 2

Refractory cases:

• Hypothalamic deep brain stimulation has been used in treatment-refractory cases 2

PH-tic Syndrome Treatment

When both conditions coexist:

• Treat each component separately with its respective medication 7, 8
• Indomethacin for PH component 7, 8
• Carbamazepine or lamotrigine for TN component 6, 7, 8
• Both headache types should respond completely to separate treatments 7

Critical Clinical Pearls

The indomethacin response is pathognomonic:

• Complete response to indomethacin distinguishes PH from all other headache disorders including TN 2
• Lack of response should prompt reconsideration of diagnosis 2

MRI interpretation requires clinical correlation:

• Neurovascular contact on MRI must be interpreted with clinical symptoms as both false-positive and false-negative results occur 5, 3
• Congruence between imaging and intraoperative findings ranges 83-100% 5

Bilateral symptoms are atypical:

• Both TN and PH are characteristically unilateral and side-locked 1, 5, 2
• Bilateral presentation warrants expanded differential diagnosis and investigation for secondary causes 5