What are the appropriate diagnostic tests and possible diagnoses for a patient presenting with diplopia (double vision), decreased vision in one eye, conversion disorder, balance loss with a wide-based gait, temporal headache, and hyperglycemia (elevated blood sugar level of 170)?

Urgent Neurological Evaluation Required for Suspected Posterior Circulation Ischemia

This patient requires immediate emergency department referral and neuroimaging with MRI brain and MRA/CTA of head and neck vessels to evaluate for posterior circulation stroke or transient ischemic attack, as the constellation of diplopia, vision loss, balance disturbance with wide-based gait, and temporal headache suggests vertebrobasilar insufficiency or brainstem pathology. 1, 2

Critical Diagnostic Approach

Immediate Neuroimaging is Mandatory

• Brain MRI with diffusion-weighted imaging (DWI) is the examination of choice to identify acute ischemic lesions in the posterior circulation, which is superior to CT for detecting brainstem and cerebellar infarcts 1, 2
• MRA or CTA of head and neck vessels must be performed to evaluate for vertebrobasilar insufficiency, carotid stenosis, or arterial dissection 1, 2
• The bilateral nature of symptoms (diplopia affecting both eyes, balance loss) strongly suggests posterior circulation involvement rather than isolated cranial nerve pathology 2
• Direct transport to emergency department or stroke center is necessary without attempting further outpatient examinations 2

Hyperglycemia as a Confounding Factor

The blood sugar of 170 mg/dL warrants consideration but is unlikely to be the primary cause:

• Hyperglycemic hemianopia typically presents with homonymous hemianopia (not diplopia) and requires severe hyperglycemia (often >500 mg/dL) with characteristic MRI findings showing cortical high signal and subcortical low signal 3, 4
• While hyperglycemia can cause reversible visual field defects, the combination of diplopia, balance loss, and wide-based gait points to structural brainstem/cerebellar pathology rather than metabolic derangement 3, 4
• However, diabetes is a risk factor for microvascular cranial nerve palsies, so glucose control should still be addressed 1

Differential Diagnosis Priority

Most Likely: Posterior Circulation Stroke/TIA

• Bilateral visual symptoms with balance disturbance and wide-based gait represent a neurological emergency with high stroke risk in the vertebrobasilar territory 2
• The wide-based gait specifically suggests cerebellar involvement, which is supplied by the posterior circulation 2
• Temporal headache can accompany vertebrobasilar ischemia 1
• Stroke risk is maximal within the first few days after symptom onset, making this time-critical 2

Alternative Considerations Requiring Urgent Imaging

• Space-occupying lesion (posterior fossa tumor, cerebellar mass) causing increased intracranial pressure with cranial nerve involvement and ataxia 5
• Demyelinating disease (multiple sclerosis) presenting with brainstem syndrome 5
• Basilar artery aneurysm or dissection causing mass effect on cranial nerves III, IV, or VI 1
• Cavernous sinus pathology if diplopia is from cranial nerve involvement, though less likely given the balance symptoms 1

Essential Clinical Examination Elements

Ophthalmologic Assessment

• Complete visual acuity testing to detect vision-threatening pathology 5
• Pupillary examination to identify afferent defects (suggesting optic nerve involvement) or efferent defects (suggesting third nerve palsy) 1, 5
• Detailed sensorimotor examination demonstrating alignment in multiple gaze positions to localize which cranial nerve(s) are affected 1
• Fundoscopic examination to assess for papilledema (suggesting increased intracranial pressure) or optic atrophy 1

Neurological Assessment

• Assess for other cranial neuropathies (facial weakness, facial sensation loss, hearing changes) that would localize to brainstem 1
• Cerebellar testing including finger-to-nose, heel-to-shin, and gait assessment to confirm cerebellar involvement 2
• Vital signs monitoring for bradycardia or heart block, which with nausea/vomiting could indicate oculocardiac reflex from muscle entrapment (though less likely without trauma history) 1

Laboratory and Cardiac Workup

• ESR and CRP should be measured if temporal headache raises concern for giant cell arteritis, though this is less common in younger patients 1, 2
• Hemoglobin A1c and fasting glucose to assess chronic glycemic control 1
• ECG and echocardiography to assess for cardioembolic sources, particularly important in patients with risk factors 2

Critical Management Pitfalls to Avoid

Do Not Delay for Outpatient Workup

• Reassurance alone is never appropriate for sudden-onset diplopia with neurological signs 5
• Attempting to complete a full ophthalmologic workup before neuroimaging risks missing time-sensitive diagnoses like stroke or tumor 5
• Nothing by mouth until swallow evaluation if brainstem involvement suspected to prevent aspiration 2

Do Not Attribute Symptoms to "Conversion" Without Excluding Organic Causes

• While "conversion issues" is mentioned in the history, conversion disorder is a diagnosis of exclusion requiring comprehensive evaluation and negative neuroimaging 6
• The presence of objective findings (wide-based gait, decreased vision) makes organic pathology far more likely than functional disorder 6
• A comprehensive and step-wise evaluation by multiple specialties and ancillary tests must rule out organic causes before considering conversion disorder 6

Do Not Assume Hyperglycemia is the Sole Cause

• The blood sugar of 170 mg/dL is elevated but not in the range typically associated with hyperglycemic hemianopia 3, 4
• The symptom complex (diplopia + ataxia + headache) is not consistent with isolated hyperglycemic visual disturbance 3, 4

Specific Cranial Nerve Localization if Isolated Palsy

If neuroimaging is negative and symptoms localize to a single cranial nerve:

Sixth Nerve Palsy (Most Common)

• Presents with incomitant esotropia greater at distance with limited abduction 1
• In elderly with vasculopathic risk factors (diabetes, hypertension), may observe for 4-6 weeks, but neuroimaging still indicated if no improvement 1
• All young patients or those with other cranial neuropathies require immediate neuroimaging 1

Third Nerve Palsy

• Pupil-involving third nerve palsy suggests vascular compression (aneurysm) and requires emergency vascular imaging 1
• Pupil-sparing palsy in diabetic patients may be microvascular, but still requires imaging to exclude structural lesions 1

Convergence Insufficiency

• Presents with exophoria greater at near, distant near point of convergence (>6 cm), and insufficient positive fusional vergence 1
• Associated with concussion or CNS disorders like Parkinson's disease 1
• However, convergence insufficiency alone does not explain balance loss or wide-based gait 1

The combination of symptoms in this patient mandates urgent stroke protocol evaluation rather than isolated strabismus workup. 2, 5