A 78-year-old man with type 2 diabetes mellitus presents to the emergency OPD in acute confusion with fever, headache, neck stiffness, vomiting and photophobia. What is your diagnosis and how will you manage this patient?

Clinical basis of the diagnosis. The most common features of acute bacterial meningitis are severe headache (84%), fever > 38 °C (74%), stiff neck (74%), GCS < 14 (71%) and nausea (62%). The classic triad occurs in only about 41–44% of adults, but 95% have at least two of the four cardinal features (fever, headache, stiff neck, altered mental status) — this patient has all four plus photophobia, so the pre-test probability is very high. Other features: cranial nerve palsies (10–20%) and seizures (~30%). Importantly, Kernig's and Brudzinski's signs are almost useless diagnostically (sensitivity 5% each; nuchal rigidity only 30%) — their absence never excludes meningitis.

The geriatric caveat. Older patients over 60 actually present with the full triad more often than younger adults (58% vs 36%), but those with underlying disease such as diabetes mellitus or cardiopulmonary disease may instead present insidiously with lethargy, confusion, anorexia, no fever and minimal meningeal signs. Confusion was present in 92% of elderly patients with pneumococcal meningitis and 78% with Gram-negative bacillary meningitis. Therefore any older patient with altered or changed mental status should be evaluated for bacterial meningitis, including consideration of CSF examination. Elderly patients are also sicker at presentation, with higher CSF protein and more abnormal imaging, and an adverse outcome occurs in 51.9% of elderly versus 7.4% of non-elderly patients.

Likely organisms. In adults 65 years or older, the commonest pathogen is Streptococcus pneumoniae (~70%), followed by Listeria monocytogenes, Neisseria meningitidis, Haemophilus influenzae, Streptococcus agalactiae and aerobic Gram-negative bacilli. Risk factors for Listeria are age over 60, chronic steroids, alcoholism, immunosuppression, malignancy and diabetes. S. pneumoniae carries the highest mortality and the highest rate of neurological sequelae (at least one major sequela in 24.7% of survivors). Look for an antecedent or concurrent focus — sinusitis, otitis media or pneumonia.

Differential diagnosis to state briefly. Viral (aseptic) meningitis — enterovirus, HSV-2, VZV, West Nile virus (elderly patients are more prone to West Nile encephalitis and to bacterial rather than viral disease); HSV encephalitis; tuberculous meningitis (very important in India — subacute course, cranial nerve palsies, basal exudates, hydrocephalus); cryptococcal and other fungal meningitis in the immunosuppressed; subarachnoid haemorrhage (thunderclap headache, neck stiffness, no fever early); brain abscess, subdural empyema; cerebral malaria; drug-induced aseptic meningitis; and delirium from any systemic cause including hypoglycaemia and hyperosmolar state in this diabetic.

Immediate emergency actions (first 15 minutes). Airway, breathing, circulation; oxygen; large-bore IV access; capillary blood glucose immediately (hypoglycaemia is the great mimic); vital signs; GCS; examine for petechial or purpuric rash (meningococcaemia), papilloedema, focal deficits, cranial nerve palsies and a septic focus in ear, sinuses and chest. Take blood cultures, then move directly to lumbar puncture or, if that must be deferred, to antibiotics. Treatment must never be delayed for imaging or for the lumbar puncture — the "one-hour window" is the accepted target for the first antibiotic dose.

Investigations. Blood cultures (before antibiotics), complete blood count, blood glucose (mg/dL), urea and creatinine (mg/dL), sodium and potassium (mEq/L), calcium (mg/dL), liver function tests, coagulation profile, CRP or procalcitonin, arterial blood gas and lactate, HbA1c, chest radiograph, HIV serology, and blood film for malaria where relevant. The diagnosis rests on CSF examination after lumbar puncture — send opening pressure, cell count with differential, protein, glucose with a paired blood glucose for the CSF:serum ratio, Gram stain, culture with antimicrobial susceptibility testing, and PCR / multiplex meningitis-encephalitis panel. Add CSF CBNAAT and adenosine deaminase if tuberculosis is suspected, and India ink and cryptococcal antigen if fungal disease is suspected.

When to do CT before lumbar puncture. Cranial imaging should not be performed routinely. Obtain CT first only if there is immunosuppression, known CNS disease, focal neurological deficit, new-onset seizure, papilloedema or a markedly depressed conscious level. In those situations, start empirical antibiotics (with dexamethasone) before scanning. Where imaging is not available, the lumbar puncture should be deferred until such features resolve — but antibiotics are still given immediately, and the LP performed as soon as it is safe.

Empirical antimicrobial therapy. For a patient over 50 years with suspected community-acquired bacterial meningitis, the recommended empirical regimen is vancomycin + ampicillin + a third-generation cephalosporin (ceftriaxone or cefotaxime). The cephalosporin covers pneumococcus and meningococcus, ampicillin covers Listeria (which cephalosporins do not cover — a classic examiner trap), and vancomycin covers penicillin- or cephalosporin-resistant pneumococci. If the Gram stain shows Gram-positive diplococci, treat as pneumococcal with vancomycin plus a third-generation cephalosporin. De-escalate once culture and susceptibility results are available. Adult CNS doses from the textbook are given in the table below.

Adjunctive dexamethasone. Bacterial lysis by antibiotics triggers a subarachnoid inflammatory response that drives morbidity and mortality. In a randomised double-blind trial of 301 adults, adjunctive dexamethasone reduced unfavourable outcomes and death, with the greatest benefit in pneumococcal meningitis and in moderate-to-severe disease by admission GCS. Give dexamethasone 0.15 mg/kg every 6 hours for 4 days, with or just before the first antibiotic dose. Key qualifications: IDSA advises against starting it once antibiotics have already been given, whereas the 2016 European guideline allows up to 4 hours and the UK guideline up to 12 hours after the in cryptococcal meningitis; benefit is not seen in resource-poor settings with a high burden of advanced HIV; and it may reduce CSF penetration of vancomycin and has been linked to delayed cerebral injury.

Supportive care, complications, prognosis and prevention. Nurse in a high-dependency area with neurological observations; manage raised intracranial pressure (head-up 30°, mannitol or hypertonic saline as a temporising measure; glycerol is not recommended); treat seizures; give maintenance isotonic fluids without routine fluid restriction, but allow moderate restriction if SIADH develops without hypovolaemia; monitor sodium closely; use an insulin infusion or basal-bolus regimen targeting roughly 140–180 mg/dL and stop metformin during acute illness; give VTE prophylaxis and pressure-area care; and apply the delirium bundle throughout, since confusion will persist after the infection is controlled. Watch for hearing loss, seizures, hydrocephalus, cerebral infarction, septic shock and cognitive impairment. Prevention: all adults 65 years or older should receive pneumococcal vaccination (both conjugate and polysaccharide vaccines as per schedule), as should those with asplenia, CSF leak, cochlear implants or immunosuppression. Give chemoprophylaxis to close contacts if meningococcal disease is confirmed.

WHO guidelines on meningitis diagnosis, treatment and care (2025) — the first global WHO guideline on clinical management of acute community-acquired meningitis, developed under the Defeating meningitis by 2030 road map (WHA73.9) and written specifically to be implementable in low- and middle-income countries. Points of direct examination value: Lumbar puncture as early as possible, preferably before antimicrobials; CSF Gram stain, cell count, protein, glucose and CSF:blood glucose ratio are strongly recommended, with CSF PCR strongly recommended in addition (culture with susceptibility testing remains the gold standard). Cranial imaging is strongly recommended against routinely; CT before LP only for GCS < 10, focal signs, cranial nerve deficits, papilloedema, new-onset seizures in adults, or severe immunocompromise — and treatment must not be delayed for it. Empirical regimen: IV ceftriaxone or cefotaxime, with ampicillin or amoxicillin added whenever a Listeria risk factor is present — explicitly including age over 60 and diabetes mellitus, exactly as in this patient. Vancomycin is added conditionally where pneumococcal resistance is prevalent (rifampicin is an alternative, but only where the tuberculosis burden is low). Chloramphenicol with ampicillin is the fallback if cephalosporins are unavailable. Corticosteroids are now a strong recommendation with the first antibiotic dose in non-epidemic settings where LP can be performed, to be stopped if the CSF is not consistent with bacterial meningitis or if an organism other than S. pneumoniae or H. influenzae type b is identified; maximum duration 4 days. Dexamethasone is the steroid of choice, but hydrocortisone or methylprednisolone may substitute at equivalent dose. Duration: where no pathogen is identified, empirical therapy may be stopped at 7 days if the patient has clinically recovered (afebrile, normal vitals, normal mental status for at least 48 hours). Sequelae: every patient should be reviewed for sequelae before discharge and again within 4 weeks, with formal audiological screening before discharge and early rehabilitation — a strong recommendation and an easy extra mark. Glycerol is recommended against; routine fluid restriction is recommended against.

Dexamethasone must be stopped once Listeria is identified. A prospective nationwide Dutch cohort (eClinicalMedicine 2023) of 162 adults with community-acquired Listeria monocytogenes meningitis found a case fatality of 31% and an unfavourable outcome in 56%, with age and the standard adjunctive dexamethasone regimen as independent predictors of both unfavourable outcome and death. This confirms the earlier French MONALISA signal and is now embedded in guidelines: start dexamethasone empirically, but discontinue it the moment Listeria (or Cryptococcus) is confirmed. In an older diabetic patient — who is precisely the Listeria-risk phenotype — this is the single most likely question the examiner will ask on follow-up.

How to differentiate the four delirium questions Question Pivot to use What NOT to spend words on Acute confusional state Terminology + causes + Detailed pathophysiology, prevention programmes

Numbers to memorise Item Value CAM sensitivity / specificity 94% / 89% 3D-CAM (with dementia / without) 96% & 86% / 93% & 96% Months of the year backwards (single item) Sens 83% / Spec 69% UB-2 two-item screen Sens 93% / Spec 64% DSD screens (1 / 2 / 3 items) — sensitivity 84% / 93% / 94% DSD screens — specificity 41% / 30% / 42% Delirium in ICU / medical wards / hospice / LTC 30–80% / 18–35% / 26–44% / 16% Pooled prevalence & incidence, hospitalised elderly (2025) 23.6% & 13.5% Still delirious at discharge / 1 / 3 / 6 months 45% / 33% / 26% / 21% Preventable proportion of delirium 30–40% Meningitis — headache / fever / stiff neck / GCS < 14 84% / 74% / 74% / 71% Meningitis — classic triad / at least 2 of 4 41–44% / 95% Meningitis — Kernig's / Brudzinski's / nuchal rigidity sensitivity 5% / 5% / 30% S. pneumoniae share of meningitis in adults ≥ 65 y ~70% Listeria meningitis case fatality (2023 cohort) 31%; unfavourable outcome 56% Dexamethasone regimen 0.15 mg/kg 6-hourly × 4 days

Named traps in this set Trap: writing that CAM diagnoses delirium. It screens; DSM-5/ICD-10 diagnose. Trap: writing the CAM algorithm as "any two features". It is (1 AND 2) + (3 OR 4), with features 1 and 2 mandatory. Trap: equating delirium with agitation. Hypoactive delirium is commonest. Trap: prescribing a benzodiazepine for restlessness — it causes and prolongs delirium. Trap: physical restraint as a safety measure — it is an independent risk factor. Trap: relying on Kernig's and Brudzinski's signs to exclude meningitis (5% sensitivity). Trap: omitting ampicillin from the empirical regimen in an older or diabetic patient — cephalosporins miss Listeria. Trap: continuing dexamethasone after Listeria is isolated — it increases mortality. Trap: delaying the first antibiotic dose for a CT scan or lumbar puncture. Trap: forgetting to check capillary glucose in a confused diabetic before doing anything else.

Indian context lines to add Under-recognition: Indian referral-based studies detect delirium in under 1% of inpatients, while CAM-ICU screening finds ~30% of elderly ICU patients delirious, ~45% of them hypoactive — the strongest argument for routine tool-based screening rather than waiting for a psychiatry referral. Tuberculous meningitis must appear in every Indian differential for fever with confusion and neck stiffness — send CSF CBNAAT and ADA alongside routine studies. Rifampicin caution: WHO 2025 permits rifampicin instead of vancomycin for resistant pneumococcus only in low tuberculosis-burden settings — in India, vancomycin is preferred. Alcohol withdrawal is a very common and under-declared cause of ward delirium in Indian men — always give parenteral thiamine before glucose. Family attendants at the bedside are the norm in Indian wards; formally enlisting them for orientation, hydration, feeding and mobilisation delivers an evidence-based delirium bundle at almost no cost. Vandana Card for those aged 70 and above; adult pneumococcal vaccination is not part of the Universal Immunization Programme and remains an out-of-pocket, opportunistic intervention — a legitimate policy-gap comment.

Fifteen-second answer skeletons Any delirium question: Define (acute, fluctuating, inattention, medical cause) → Subtypes → SIFH → Predisposing + Precipitating (DELIRIUM IS VERY PAINFUL) → Differentiate from dementia → Screen (CAM/4AT) then diagnose (DSM-5) → Targeted workup → Treat the cause → Non-pharmacologic bundle + T-A-DA → Drugs only for imminent harm → Prevent (HELP/mHELP/ABCDEF) → Prognosis and follow-up. Any acute meningitis question: Recognise (triad + meningism, but triad in <50%) → Resuscitate + glucose → Blood cultures → Decide on CT (only if GCS < 10, focal signs, papilloedema, seizure, immunocompromise) → Lumbar puncture → Dexamethasone + antibiotics within 1 hour (never delayed) → Empirical vancomycin + ampicillin + ceftriaxone over 50 years → De-escalate on culture; stop steroid if not pneumococcal → Supportive care, ICP, sodium, glycaemia, delirium bundle → Complications → Audiology and sequelae review before discharge → Vaccination and contact prophylaxis.