Differential Diagnosis for Unilateral Headache Behind One Eye
The differential diagnosis for unilateral headache behind the eye must prioritize life-threatening conditions first, then systematically consider primary headache disorders (especially trigeminal autonomic cephalalgias and migraine), followed by neuropathic, vascular, and ophthalmologic causes.
Critical Red Flags to Rule Out Immediately
Giant Cell Arteritis (Age >50)
- Must be excluded urgently in patients over 50 years old to prevent irreversible blindness 1
- Look for: temporal region pain, jaw claudication, visual symptoms, fever, myalgia, absent temporal artery pulse
- Check: ESR and C-reactive protein (typically elevated)
- Action: Urgent temporal artery biopsy and start high-dose corticosteroids (minimum 40 mg daily) within 2 weeks 1
Secondary Causes Requiring Imaging
- Progressive neuropathic pain suggests possible malignancy (primary or metastatic cancer) 1
- Posterior communicating artery aneurysm 2
- Obtain MRI including pituitary fossa for atypical presentations 1
Primary Headache Disorders (Most Common)
Migraine
Migraine is the most common cause of recurrent unilateral periorbital headache 3
Diagnostic criteria require at least 5 attacks with:
- Duration: 4-72 hours untreated
- Two of four characteristics: unilateral location, pulsating quality, moderate-severe intensity, aggravation by routine activity
- At least one: nausea/vomiting OR photophobia and phonophobia 3
Key distinguishing features:
- Aura symptoms spread gradually over ≥5 minutes (vs. sudden onset in TIA) 3
- May have visual, sensory, speech, or motor aura preceding headache by up to 60 minutes 3
Trigeminal Autonomic Cephalalgias (TACs)
These are strictly unilateral and easily mistaken for each other but have distinct treatment responses 4
Cluster Headache
- Severe orbital/supraorbital/temporal pain
- Duration: 15-180 minutes
- Frequency: Once every 2 days to 8 times daily
- Prominent ipsilateral autonomic features: lacrimation, rhinorrhea, conjunctival injection, nasal congestion, eyelid edema, facial sweating 4, 5
- Patient typically restless during attacks
SUNCT/SUNA Syndromes
- Rapid attacks lasting seconds to several minutes
- Up to 200 attacks daily with no refractory period
- Sharp, stabbing, moderate-severe pain
- Mostly spontaneous, some light touch evoked
- Autonomic features: tearing, red eye, rhinorrhea, ear fullness 1
- Treatment: Lamotrigine (not carbamazepine) 1
Neuropathic Pain Syndromes
Trigeminal Neuralgia
Characterized by sudden, unilateral, severe, brief stabbing pain in trigeminal nerve distribution 1
Distinguishing features:
- Electric shock-like quality
- Provoked by light touch to trigger zones
- Attacks last seconds to 2 minutes
- Pain-free intervals between attacks
- First-line treatment: Carbamazepine (oxcarbazepine has fewer side effects) 1
- Neurosurgical referral indicated early if medication fails 1
Glossopharyngeal Neuralgia
- Same characteristics as trigeminal neuralgia but different location
- Pain in ear only (can mimic TMD) or posterior tongue
- Rare association with syncope (vagal proximity) 1
Post-Traumatic Neuropathic Pain
- History of major trauma or dental procedures
- Continuous aching/burning pain with touch sensitivity
- Dysesthesia in affected area
- Manage as standard neuropathic pain with tricyclic antidepressants 1
Musculoskeletal Causes
Temporomandibular Disorders (TMD)
Most common non-dental chronic facial pain 1
- Can be unilateral or bilateral
- Involves muscles of mastication
- Aggravated by prolonged chewing, jaw movement
- May have jaw clicking, locking, limited opening
- Associated with other chronic pain conditions
- Treatment: Early reassurance, physiotherapy, night splints 1
Critical pitfall: TMD in patients >50 can mimic giant cell arteritis—always check ESR/CRP 1
Ophthalmologic Causes
Acute Angle-Closure Glaucoma
- Sudden severe eye pain
- Decreased vision, halos around lights
- Red eye, mid-dilated fixed pupil
- Requires immediate ophthalmology referral
Corneal Disease (Most Common Ophthalmic Cause)
- Ocular surface disease
- Foreign body sensation
- Photophobia, tearing 2
Orbital Masses and Intraocular Inflammation
- Progressive symptoms
- Associated visual changes
- Abnormal eye examination 2
Sinus-Related
Acute Sinusitis
- Frontal or maxillary sinus involvement
- Purulent nasal discharge
- Facial tenderness to palpation
- Fever may be present 5
Persistent Idiopathic Facial Pain (Atypical Facial Pain)
Diagnosis of exclusion when symptoms don't fulfill other criteria 1
- Non-anatomical distribution
- Continuous but may have pain-free days
- Often bilateral, can be extraoral and intraoral
- History of other chronic pain, poor coping skills, mood disturbance
- Treatment: Tricyclic antidepressants plus cognitive behavioral therapy 1
Diagnostic Approach Algorithm
- Age >50? → Check ESR/CRP immediately to rule out giant cell arteritis
- Episodic or continuous pain?
- Episodic: Consider TACs, migraine, trigeminal neuralgia
- Continuous: Consider TMD, persistent idiopathic facial pain, post-stroke pain
- Autonomic features present? → TACs (cluster, SUNCT/SUNA)
- Electric shock quality with trigger zones? → Trigeminal neuralgia
- Pulsating with nausea/photophobia? → Migraine
- Jaw symptoms/chewing aggravation? → TMD (but rule out GCA if >50)
- Red eye/vision changes? → Ophthalmologic emergency
- Progressive symptoms? → MRI to rule out structural lesion/malignancy