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Clinical Analysis: Acute Altered Sensorium / Delirium in a 62-Year-Old Diabetic Hypertensive with Fever

Immediate Clinical Framing

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Differential Diagnosis (Priority Order)

🔴 Most Likely — Must Exclude First

🟡 Important Alternatives

🟢 Less Likely Given the History

• Intracranial hemorrhage / infarct (CT normal)
• Hepatic encephalopathy (no substance abuse, no liver disease history)
• Drug intoxication/withdrawal (no substance abuse)

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Pathophysiology Note

"The most frequent causes of global confusional states in general practice are drug intoxications and endogenous metabolic encephalopathies, mainly electrolyte and water imbalance, renal and hepatic failure, hyper- and hypoglycemia, febrile and septic states." — Adams and Victor's Principles of Neurology, 12th Ed.

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Workup Checklist

Bedside / Immediate

• ✅ Capillary blood glucose — first thing, bedside glucometer
• ✅ Vitals: BP, HR, SpO₂, temperature (exact value), respiratory rate

Blood Tests (Urgent)

Urine

• Urine dipstick + microscopy + culture (rule out urosepsis)
• Urine ketones

Imaging / Special Investigations

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Empirical Management While Awaiting Results

1. IV access + baseline bloods simultaneously
2. Check glucose stat — if <70 mg/dL → 25 mL of 50% dextrose IV immediately
3. IV fluid resuscitation (0.9% NS) — nearly always indicated (dehydration from fever + URTI)
4. If glucose significantly elevated (>250 mg/dL) → initiate insulin protocol per DKA/HHS guidelines
5. If clinically septic and source unclear → empirical antibiotics after blood/urine cultures
6. Hold nephrotoxic drugs (NSAIDs) and review antihypertensive/diabetes medications
7. Monitor urine output, vitals, GCS serially
8. Consider empirical IV acyclovir if viral encephalitis (HSV) cannot be excluded pending LP

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Key "Can't Miss" Diagnosis to Rule Out at Bedside

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Part 1: Critical Glucose Interpretation

Blood glucose 110 → 70 mg/dL

• Initial 110 mg/dL — in a known diabetic, this is deceptively "normal" but actually represents relative hypoglycemia if the patient is on antidiabetic agents (sulfonylureas, insulin). Diabetics often run higher baseline glucoses; a value of 110 in a medicated diabetic can be an early downward trend.
• Drop to 70 mg/dL — this is the hypoglycemic threshold (≤70 mg/dL = hypoglycemia by ADA definition). In a patient with altered sensorium, this is immediately actionable.

⚠️ Do NOT wait — treat the hypoglycemia NOW, regardless of the encephalitis workup. Hypoglycemia is reversible within minutes; encephalitic damage from delayed treatment is not.

Immediate Hypoglycemia Management

1. If IV access is present: 25 mL of 50% Dextrose (D50W) IV bolus → recheck glucose in 15 minutes
2. If no IV access: Glucagon 1 mg IM/SC, or oral glucose if patient can protect airway
3. Target glucose: 140–180 mg/dL (avoid overcorrection in encephalitis context — hyperglycemia worsens brain injury)
4. Start 10% Dextrose infusion to maintain glucose, especially if on long-acting sulfonylurea or insulin
5. Recheck glucose every 30–60 minutes

The altered sensorium may be partly or entirely due to hypoglycemia — reassess mental status after correction before attributing all symptoms to encephalitis.

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Part 2: Treatment for Suspected Encephalitis

The Golden Rule: Don't Wait — Treat Empirically

"Early treatment of herpes simplex encephalitis is vital as treatment with acyclovir yields the best results when administered before patients become comatose. Most patients with suspected herpes encephalitis are now treated immediately, with the drug discontinued later if the diagnosis is not confirmed." — Plum and Posner's Diagnosis and Treatment of Stupor and Coma

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Step-by-Step Management Protocol

Step 1 — Stabilise (Simultaneously with workup)

Step 2 — CT Brain (Already Done ✅ — Normal)

Step 3 — Lumbar Puncture (LP) ASAP

• Cell count + differential
• Glucose and protein
• HSV-1 and HSV-2 PCR (gold standard)
• VZV PCR
• Enterovirus PCR
• Bacterial culture and sensitivity
• India ink / cryptococcal antigen (in immunocompromised)
• Oligoclonal bands, NMDA-R antibodies (if autoimmune encephalitis suspected)
• Opening pressure

• WBC: 10–1000/mm³ (lymphocytic predominance)
• Protein: elevated (occasionally up to 870 mg/dL)
• Glucose: usually normal (low in ~5%)
• RBCs: present (hemorrhagic necrosis)

Step 4 — Start Empirical Acyclovir (DO NOT DELAY)

• Infuse over 1 hour (rapid infusion → nephrotoxicity, crystalluria)
• Ensure adequate hydration — maintain urine output >0.5 mL/kg/hr to prevent renal crystalline nephropathy
• Dose adjustment required for renal impairment (check creatinine — this patient is a known diabetic and hypertensive, renal impairment likely)

"The alkaline pH of acyclovir can cause local inflammation and phlebitis. Dose adjustment is required in patients with impaired renal glomerular filtration. Penetration into CSF is excellent." — Harrison's Principles of Internal Medicine, 22nd Ed.

Step 5 — Cover Bacterial Meningitis Simultaneously

Stop ceftriaxone and dexamethasone if CSF/cultures confirm viral etiology.

Step 6 — MRI Brain (If Not Already Done)

• Sequences: FLAIR, DWI, T2, T1 + gadolinium
• HSV pattern: Bilateral (often asymmetric) mesiotemporal lobe signal — amygdala, hippocampus, uncus, insular cortex, inferior frontal lobe
• A normal MRI early does not rule out HSV encephalitis

Step 7 — EEG

• Order EEG — especially to rule out nonconvulsive status epilepticus
• HSV encephalitis: periodic lateralized epileptiform discharges (PLEDs) from temporal lobes at ~1 Hz are highly characteristic and suggest poor prognosis
• All viral encephalitides show diffuse polymorphic slow-wave activity

Step 8 — Supportive ICU-Level Care

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When to Consider Autoimmune Encephalitis

• Anti-NMDA receptor encephalitis (most common autoimmune encephalitis)
• Send: serum and CSF NMDA-R, LGI1, CASPR2, AMPA-R antibodies
• Treatment: IV methylprednisolone 1g/day × 5 days ± IVIG ± plasma exchange

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Prognosis

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Summary of Key Orders Right Now

1. D50W 25 mL IV STAT → recheck glucose in 15 min → 10% Dextrose infusion
2. IV Acyclovir 10 mg/kg (adjusted for renal function) q8h — START NOW
3. IV Ceftriaxone 2g q12h + IV Dexamethasone 0.15 mg/kg q6h
4. Lumbar puncture (HSV PCR, cell count, glucose, protein, culture)
5. MRI Brain with FLAIR/DWI/Gadolinium
6. EEG
7. ICU admission / HDU monitoring
8. Check renal function, LFTs, CBC, electrolytes
9. Strict glucose monitoring q1h, target 140–180 mg/dL

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Glucose 110 → 70 mg/dL: Act Immediately

⚠️ Reassess sensorium after glucose correction — altered consciousness may partially or fully resolve if hypoglycemia was the primary driver.

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Suspected Encephalitis: Empirical Treatment Protocol

Core Principle: Treat first, confirm later

"Most patients with suspected herpes encephalitis are treated immediately, with the drug discontinued later if the diagnosis is not confirmed." — Plum & Posner

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Drug Treatment

Acyclovir Renal Dose Adjustment

Infuse over 1 hour + maintain good hydration → prevents renal crystalline nephropathy.

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Diagnostic Steps (Run Parallel to Treatment)

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Supportive Care

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If HSV PCR Negative → Consider Autoimmune Encephalitis

• Send NMDA-R antibodies (serum + CSF)
• Treat with IV Methylprednisolone 1 g/day × 5 days ± IVIG ± plasma exchange

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Prognosis of HSV Encephalitis

Acyclovir Dose — 50 kg Patient

10 mg × 50 kg = 500 mg IV every 8 hours (i.e., 500 mg TDS)

• Infuse each dose over 60 minutes in 100 mL NS
• Ensure urine output >0.5 mL/kg/hr (>25 mL/hr) throughout
• Adjust if CrCl <50 (as discussed — check renal function first)
• Duration: 14 days minimum → 21 days if HSV confirmed

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Lumbar Puncture — Complete CSF Send-Off

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🧫 Bottle 1 — Microbiology (2–3 mL)

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🔬 Bottle 2 — Biochemistry (1–2 mL)

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🩸 Bottle 3 — Cytology / Cell Count (1–2 mL)

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🧪 Bottle 4 — Immunology / Special (1–2 mL)

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📏 Record at Time of LP

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🩺 Also Send Simultaneously — Blood Tests

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Interpretation Quick Guide — CSF Profile

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• Acyclovir: 500 mg IV TDS (pending renal function)
• Priority CSF tests: HSV PCR, cell count, glucose + protein, bacterial culture
• Do not delay acyclovir for LP results

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Role of Vancomycin

Why it's added:

"Due to the emergence of penicillin- and cephalosporin-resistant S. pneumoniae, empirical therapy should include a combination of dexamethasone, a third/fourth-generation cephalosporin, and vancomycin, plus acyclovir, as HSV encephalitis is the leading disease in the differential." — Harrison's 22nd Ed.

Dose:

• Infuse over 60–90 minutes (rapid infusion → Red Man Syndrome)
• Monitor vancomycin trough levels (target trough: 15–20 mg/L for CNS infection)
• Dose-adjust for renal impairment — check creatinine (this patient is diabetic + hypertensive → likely CKD)
• For 50 kg patient: 750–1000 mg q8h (confirm by renal function and vancomycin levels)

When to stop:

• CSF culture grows a penicillin/cephalosporin-sensitive organism → stop vancomycin, continue ceftriaxone alone
• HSV PCR positive, no bacterial growth → stop vancomycin + ceftriaxone, continue acyclovir

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Role of Meropenem

When is meropenem used instead of ceftriaxone?

"Hospital-acquired meningitis, and particularly meningitis following neurosurgical procedures — empirical therapy should include a combination of vancomycin and meropenem." — Harrison's 22nd Ed.

"Patients who have had a recent hospitalization or surgery may benefit from broader coverage with cefepime or meropenem instead of ceftriaxone." — Rosen's Emergency Medicine

For this patient (62-year-old, community-acquired, no recent surgery):

Meropenem Dose (if used):

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Dexamethasone — Dose and Role

Role:

• Reduces neuroinflammation caused by bacterial lysis (cytokine storm from antibiotic-induced bacterial death)
• Decreases cerebral oedema, raised ICP, and vasculitis
• Proven benefit: ↓ mortality in pneumococcal meningitis, ↓ hearing loss in H. influenzae meningitis
• Must be given before or with the first antibiotic dose — giving it after reduces benefit significantly

"The first dose of steroids should be given with or 20 minutes before initiation of antibiotics in suspected adult bacterial meningitis." — Rosen's Emergency Medicine

Dose:

0.15 mg × 50 kg = 7.5 mg IV q6h × 4 days (Capped at 10 mg per dose — so 7.5 mg is the correct dose here)

When to stop dexamethasone:

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Summary: Complete Empirical Regimen for This Patient

Stop/de-escalate based on CSF PCR and culture results within 48–72 hours.

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Does Meropenem Cover Listeria and Neisseria?

Listeria monocytogenes — ❌ NO

"For all ages from 3 months onward, an alternative treatment is meropenem plus vancomycin — does not provide coverage for Listeria." — Adams and Victor's Principles of Neurology, 12th Ed.

Listeria is an intrinsically resistant organism to all cephalosporins. Meropenem has in vitro activity against Listeria but is considered clinically unreliable for CNS Listeria infection and is not recommended for this indication.

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Neisseria meningitidis — ✅ YES

"The β-lactam antibiotic meropenem is as effective as cefotaxime for meningitis caused by S. pneumoniae, N. meningitidis, and H. influenzae." — Goldman-Cecil Medicine

• N. meningitidis remains highly susceptible to penicillin G and ceftriaxone
• Meropenem is overkill for a penicillin-sensitive organism
• Ceftriaxone is preferred as first-line for meningococcal meningitis

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Practical Summary for This Patient (62M, >55 years, Diabetic)

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Bottom Line

• Meropenem covers Neisseria ✅ but NOT Listeria ❌
• In a patient >55 years old and/or diabetic — Ampicillin 2g IV q4h is mandatory to cover Listeria, regardless of whether you use ceftriaxone or meropenem
• Meropenem's main role in meningitis is as a cephalosporin substitute (allergy, nosocomial/Pseudomonal coverage), not as a Listeria agent

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How This Changes Everything

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Revised Top Diagnosis: Vertebrobasilar Ischaemia / Basilar Artery Territory Stroke

Why the pieces fit together:

"Coma, ataxia, and vertigo, which are common with vertebrobasilar (posterior circulation) stroke, are uncommon with carotid (anterior circulation) stroke." — Bradley and Daroff's Neurology in Clinical Practice

"Vertebrobasilar strokes produce unilateral or bilateral motor/sensory deficits, usually accompanied by cranial nerve and brainstem signs — vertigo, diplopia, ataxia." — Washington Manual of Medical Therapeutics

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Revised Differential Diagnosis

🔴 Top Priority

🟡 Important

🟢 Now Less Likely (but don't discard)

• HSV encephalitis — still possible; the fever and URTI remain; run parallel workup
• Metabolic encephalopathy — still check glucose, electrolytes

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The Critical Investigation Now

⚠️ MRI Brain is No Longer Optional — It is Urgent

A normal CT does NOT rule out posterior circulation stroke. This is the most common diagnostic pitfall in brainstem infarction.

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Additional Bedside Examination Points

HINTS Exam (Bedside — Very Important)

A normal head impulse test + direction-changing nystagmus = CENTRAL cause — treat as stroke.

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Revised Management Priorities

Immediate

1. Urgent MRI Brain + MRA (DWI, FLAIR, T2, GRE, MR angiography)
2. Neurology team involvement immediately
3. Check BP — if severely elevated → hypertensive emergency contributing to PRES/haemorrhage
4. Correct hypoglycaemia (glucose was 70 — treat as before)
5. Monitor vitals + GCS serially — basilar occlusion can deteriorate rapidly to coma

If Basilar Artery Occlusion Confirmed on MRI/MRA:

• Thrombolysis (IV tPA) if within window (4.5 hours from last known well)
• Mechanical thrombectomy — extended window up to 24 hours for basilar artery occlusion (differs from anterior circulation)
• Antiplatelet / anticoagulation depending on mechanism (atherosclerosis vs cardioembolic vs dissection)

If PRES:

• Aggressive BP control (IV labetalol or nicardipine)
• Remove precipitating cause

Encephalitis cover:

• Do not abandon acyclovir + antibiotics until MRI clarifies — run the infectious workup in parallel

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Summary: The New Clinical Story

62M + Diabetes + Hypertension
  ↓
Chronic vertebrobasilar insufficiency
(1 year of recurrent vertigo + dysarthria = posterior circulation TIAs)
  ↓
Intercurrent viral illness (fever, URTI)
  ↓
Haemodynamic compromise / plaque rupture
  ↓
ACUTE BASILAR TERRITORY ISCHAEMIA
= Altered sensorium (RAS involvement)
  ↓
CT BRAIN NORMAL ← Expected in posterior fossa stroke
  ↓
MRI BRAIN + MRA URGENTLY

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What Normal Plantar + No Limb Weakness Tells Us

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Revised Localisation

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This Pattern Now Points Strongly Toward:

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🔴 1. Chronic Cerebellar / Posterior Fossa Disease with Acute Decompensation

• Cerebellar ataxia causes dysarthria (scanning/slurred speech) without limb weakness
• Vestibular dysfunction causes vertigo without motor signs
• An intercurrent illness (fever, dehydration, metabolic stress) acutely decompensates a previously compensated cerebellar condition

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🔴 2. Wernicke's Encephalopathy (Must Actively Exclude)

• Encephalopathy (confusion, disorientation) ✅
• Ataxia / cerebellar signs (vertigo, gait disturbance) ✅
• Ophthalmoplegia (nystagmus, gaze palsy) — ask specifically

• Poor nutritional intake
• Thiamine (Vitamin B1) depletion
• IV dextrose without thiamine supplementation precipitates acute Wernicke's

⚠️ If you gave D50W for hypoglycaemia without giving thiamine first — Wernicke's can be precipitated or worsened.

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🟡 3. Metabolic Encephalopathy Superimposed on Chronic Cerebellar Disease

• Infection (fever, URTI → septic encephalopathy)
• Hypoglycaemia (glucose dropped to 70)
• Dehydration and electrolyte disturbance
• Any of the above on a vulnerable cerebellum

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🟡 4. PRES (Posterior Reversible Encephalopathy Syndrome)

• Known hypertensive + diabetic
• Altered sensorium, normal CT (PRES is invisible on CT)
• Posterior circulation involvement
• No motor signs — PRES typically spares motor tracts
• MRI FLAIR will show posterior white matter oedema

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Revised Investigation Priority

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Critical Immediate Action — Thiamine

In any confused patient with diabetes, chronic illness, or poor nutrition — always give thiamine before or with glucose. Glucose load without thiamine precipitates acute Wernicke's encephalopathy by depleting the last reserves of thiamine needed for glucose metabolism.

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Updated Clinical Summary

62M | DM | HTN
Chronic: Vertigo + Dysarthria × 1 year
         ↓
   Cerebellar syndrome (chronic)
   [No weakness, No pyramidal signs]
         ↓
Acute: Fever + Hypoglycaemia + ??Thiamine depletion
         ↓
Acute decompensation → Altered sensorium + Disorientation
         ↓
Leading diagnoses:
1. Wernicke's encephalopathy (give thiamine NOW)
2. Metabolic encephalopathy on chronic cerebellar disease
3. PRES (hypertension)
4. Paraneoplastic cerebellar degeneration
         ↓
MRI Brain (FLAIR, DWI, T1 for mamillary bodies)
+ Thiamine supplementation empirically

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Non-Alcoholic Status Does NOT Rule Out Wernicke's

"While frequently associated with chronic alcohol misuse, Wernicke-Korsakoff syndrome can occur in any clinical situation that is caused by or causes malnutrition." — Kaplan & Sadock's Comprehensive Textbook of Psychiatry

"A significant number of elderly hospitalized patients have evidence of moderate to severe thiamine deficiency... the disease can be precipitated by giving vitamin-free glucose infusions to chronically malnourished subjects." — Plum and Posner's Diagnosis and Treatment of Stupor and Coma

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Non-Alcoholic Causes of Wernicke's Encephalopathy

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Where This Patient Sits Now

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Revised Differential (Non-Alcoholic)

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Action — What to Do Right Now

1. ⚠️ Give IV Thiamine IMMEDIATELY

"Its absorption orally is unreliable in malnourished patients — it must be supplied by IV or IM injection. Prompt diagnosis and treatment is crucial to minimise lasting deficits." — Plum and Posner

• Give before any further dextrose
• Risk of IV thiamine: rare anaphylaxis (very uncommon with slow infusion)
• Do not delay for thiamine levels — treat empirically

2. Bedside Eye Examination — Look for Wernicke's Triad

"Behavioral symptoms can be attributed to Wernicke's disease only when accompanied by nystagmus, oculomotor paralysis, and impaired vestibulo-ocular responses that are subsequently reversed by thiamine treatment." — Plum and Posner

3. MRI Brain Urgently

• T1 with contrast — mamillary body and periaqueductal grey hyperintensity = Wernicke's pathognomonic finding
• FLAIR — PRES, encephalitis
• DWI — acute ischaemia

4. Blood Tests

• Serum thiamine level (before giving thiamine if possible — but don't delay treatment for it)
• B12, folate
• TFTs
• Serum lactate (thiamine deficiency → lactic acidosis)
• Tumour markers + CT chest/abdomen if paraneoplastic suspected

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Bottom Line

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Cerebral / Severe Malaria — Why Consider It Here?

• Fever + altered sensorium → think cerebral malaria if from or travelled to an endemic area
• Diabetes → increased risk of severe malaria complications

"Any patient with a change in mental status or repeated seizure in the setting of fulminant malaria has cerebral malaria... caused by Plasmodium falciparum... fever, lethargy, neurologic signs... In adults, nonspecific febrile illness progresses to coma over several days." — Harrison's 22nd Ed.

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Artesunate — Drug of Choice for Severe/Cerebral Malaria

"Parenteral artesunate reduced severe falciparum malaria mortality by 35% in Asian adults vs quinine. Artesunate is the drug of choice for all patients with severe malaria everywhere." — Harrison's 22nd Ed.

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Dose of IV Artesunate — Severe/Cerebral Malaria

For adults (weight ≥20 kg):

For this patient (50 kg):

2.4 mg × 50 kg = 120 mg IV

Artesunate is given by IV injection (bolus). Can also be given IM if IV not immediately available.

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For children <20 kg:

• Use 3 mg/kg per dose (higher weight-based dose as younger children have faster drug clearance)

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Switch to Oral Once Patient Improves

Minimum 24 hours of IV artesunate before switching to oral, regardless of clinical improvement.

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If IV Artesunate Unavailable — Alternatives (in order of preference)

Artemether is erratically absorbed IM and does not confer the same survival benefit as artesunate. Quinine has a narrow therapeutic window — risk of hypoglycaemia, QT prolongation, cinchonism.

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Artemisinin Resistance Area (Southeast Asia)

If patient is from or travelled to Greater Mekong Subregion (Myanmar, Cambodia, Vietnam, Thailand):

• Give artesunate + quinine together at full doses (precautionary dual therapy for presumed resistance)

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Important Adjuncts in Cerebral Malaria

⚠️ Steroids are contraindicated in cerebral malaria — unlike bacterial meningitis where dexamethasone is beneficial.

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Summary Card

SEVERE / CEREBRAL MALARIA
Drug of choice: IV Artesunate

50 kg patient:
→ 120 mg IV STAT (0h)
→ 120 mg IV at 12h
→ 120 mg IV at 24h
→ 120 mg IV once daily until oral tolerated

Then switch to oral ACT (artemether-lumefantrine)

DO NOT use steroids
DO correct hypoglycaemia
DO add broad-spectrum antibiotics