What could be causing an 82-year-old man's difficulty in holding his head up and keeping his eyes open?

Differential Diagnosis: Difficulty Holding Head Up and Keeping Eyes Open in an 82-Year-Old Man

This presentation most likely represents myasthenia gravis with isolated neck extensor weakness (dropped head syndrome) and ptosis, which requires urgent evaluation with an edrophonium test or single-fiber EMG and serum acetylcholine receptor antibodies. 1

Primary Diagnostic Consideration: Myasthenia Gravis

Myasthenia gravis can present with dropped head sign as the sole or predominant symptom, particularly in older adults, and may remain isolated without progression to other muscle groups. 1 The combination of:

• Difficulty holding the head up (neck extensor weakness/dropped head sign)
• Difficulty keeping eyes open (ptosis)
• Age 82 years

This triad strongly suggests myasthenia gravis, which should be the first diagnosis to exclude given its treatability and potential for rapid deterioration. 1

Key Diagnostic Features to Assess

Variable ptosis that worsens with sustained upgaze or fatigue is pathognomonic for myasthenia gravis. 2, 3 Specifically evaluate:

• Ice test: Apply ice pack to closed eyelid for 2 minutes; improvement in ptosis suggests myasthenia gravis 2
• Fatigability: Ptosis worsening after sustained upgaze for 60 seconds 2, 3
• Diurnal variation: Symptoms typically worse later in the day 1
• Diplopia: May be present but not always, particularly if ptosis is severe enough to occlude visual axis 4

Immediate Diagnostic Workup

1. Serum acetylcholine receptor antibodies (positive in 80-90% of generalized MG) 1
2. Edrophonium (Tensilon) test or neostigmine test for rapid bedside confirmation 1
3. Single-fiber EMG if antibodies negative but clinical suspicion remains high 1
4. Chest CT to evaluate for thymoma once diagnosis confirmed 1

Critical Alternative Diagnoses to Exclude

Progressive Supranuclear Palsy (PSP)

This is a crucial differential given the age and presentation. PSP classically presents with: 5

• Vertical gaze palsy (especially downward gaze restriction) - this is the distinguishing feature 5
• Difficulty with eyelid opening (apraxia of eyelid opening, not true ptosis) 5
• Axial rigidity with neck extension (not flexion/dropped head) 5
• Bradykinesia and postural instability with backward falls 5
• Pseudobulbar palsy with dysphagia 5
• Poor response to levodopa 5

Key distinction: PSP causes difficulty opening eyes due to apraxia, not ptosis, and causes neck rigidity in extension, not dropped head. 5

Oculomotor (Third Nerve) Palsy

Third nerve palsy presents with ptosis plus specific ocular motility deficits, not isolated ptosis. 4 Look for:

• Pupillary involvement (dilated, poorly reactive pupil suggests aneurysm requiring urgent imaging) 4, 3
• Eye positioned "down and out" due to preserved lateral rectus and superior oblique function 4
• Diplopia with both horizontal and vertical components 4

If pupil-involving third nerve palsy is present, obtain urgent MRA or CTA to rule out posterior communicating artery aneurysm. 3

Giant Cell Arteritis (GCA)

Given the patient's age (82 years), GCA must be considered, particularly if visual symptoms are present. 4 Assess for:

• Jaw claudication (positive LR 4.90, highly specific at 92.3%) 4
• Scalp tenderness (positive LR 1.85) 4
• Temporal headache 4
• Constitutional symptoms (fever, weight loss, malaise) 4
• ESR >60 mm/h strongly suggests GCA 4

If GCA is suspected, initiate high-dose glucocorticoids immediately before awaiting temporal artery biopsy results. 4

Secondary Considerations in Elderly Patients

Orthostatic Hypotension and Syncope-Related Falls

Elderly patients frequently present with falls that may be syncope-related, and amnesia for loss of consciousness occurs in up to 40% of elderly patients. 4 Evaluate:

• Orthostatic vital signs (supine and after 3 minutes standing) 4
• Polypharmacy review (diuretics, β-blockers, calcium antagonists, ACE inhibitors, antipsychotics, tricyclics) 4
• Carotid sinus massage (both supine and upright, as up to one-third of elderly show diagnostic response only when upright) 4

Parkinson's Disease and Related Disorders

Axial rigidity with camptocormia (forward trunk flexion) can occur in Parkinson's disease, but: 5

• Typically accompanied by other parkinsonian features (tremor, bradykinesia, shuffling gait) 5
• Neck flexion (dropped head) is less common than truncal flexion 5
• Would not explain isolated ptosis 5

Diagnostic Algorithm

1. Immediate bedside assessment:

   • Ice test for ptosis 2
   • Sustained upgaze for fatigability 2, 3
   • Pupillary examination (rule out third nerve palsy) 4, 3
   • Extraocular motility testing (rule out PSP, third nerve palsy) 4, 3
   • Cover/uncover test for ocular misalignment 3

2. If myasthenia gravis suspected (variable ptosis, fatigability, positive ice test):

   • Acetylcholine receptor antibodies 1
   • Edrophonium test 1
   • Single-fiber EMG if antibodies negative 1

3. If third nerve palsy suspected (ptosis with ocular motility deficit):

   • Urgent MRA/CTA if pupil-involving 3
   • MRI brain if pupil-sparing (evaluate for microvascular ischemia) 4

4. If PSP suspected (vertical gaze palsy, axial rigidity, poor levodopa response):

   • MRI brain (midbrain atrophy, "hummingbird sign") 5
   • Neurology referral 5

5. If GCA suspected (age >60, jaw claudication, temporal headache):

   • Immediate ESR and CRP 4
   • Start high-dose prednisone (40-60 mg daily) before biopsy if high suspicion 4
   • Temporal artery biopsy within 1-2 weeks 4

6. Orthostatic assessment in all elderly patients:

   • Orthostatic vital signs 4
   • Medication review 4
   • Carotid sinus massage (if no carotid bruits) 4

Common Pitfalls to Avoid

• Overlooking variable ptosis that worsens with fatigue, which may indicate myasthenia gravis 2, 3
• Failing to assess pupillary abnormalities, which may indicate third nerve palsy requiring urgent vascular imaging 4, 3
• Dismissing symptoms as "normal aging" without proper evaluation for treatable causes 4
• Not performing upright carotid sinus massage in elderly patients, as one-third show diagnostic responses only when upright 4
• Confusing PSP's apraxia of eyelid opening with true ptosis from myasthenia gravis 5
• Delaying treatment of GCA while awaiting biopsy results in patients with high clinical suspicion 4