Normal Pressure Hydrocephalus (NPH)

A 75 year old male with a history of hypertension and type 2 diabetes mellitus presents to the neurology clinic with complaints of difficulty walking, memory problems, and urinary incontinence over the past year. His wife reports that he has become increasingly forgetful, often misplacing items and repeating conversations, although he still recognizes family members and can perform daily activities. She also notes urinary urgency progressing to incontinence. On examination, the patient has a slow, broad-based gait with difficulty initiating steps and a tendency to appear as if his feet are “stuck to the floor,” consistent with a magnetic gait. There are no focal neurological deficits, and deep tendon reflexes are normal. There are no features of increased intracranial pressure such as headache, vomiting, or papilledema. CT scan of the head shows ventriculomegaly disproportionate to cortical atrophy. Lumbar puncture reveals a normal opening pressure. Diagnosis?

Diagnosis is Normal Pressure Hydrocephalus (NPH).

1. Definition

Normal pressure hydrocephalus is characterized by ventricular enlargement with normal cerebrospinal fluid opening pressure, leading to the classic clinical triad.

2. Pathophysiology

1. Impaired CSF absorption at the arachnoid granulations
2. Results in ventricular dilation without sustained elevation of intracranial pressure
3. Causes periventricular white matter dysfunction affecting gait, cognition, and bladder control

3. Clinical Features

3.1 Classic Triad

1. Gait disturbance
2. Cognitive impairment
3. Urinary incontinence

3.2 Gait Features

1. Magnetic gait
2. Broad-based, slow gait
3. Difficulty initiating steps

3.3 Cognitive Features

1. Subcortical dementia with slowed processing and executive dysfunction
2. Relatively preserved recognition in early stages

3.4 Urinary Features

1. Urinary urgency progressing to incontinence

4. Diagnostic Evaluation

4.1 Neuroimaging

1. Ventriculomegaly disproportionate to cortical atrophy
2. May show DESH pattern
3. Evans index > 0.3 supports diagnosis

4.2 Lumbar Puncture

1. Normal opening pressure

4.3 CSF Tap Test

1. Removal of 30 to 50 mL of CSF
2. Improvement in gait or cognition supports diagnosis

5. Key Diagnostic Insight

Gait disturbance + urinary incontinence + cognitive decline with ventriculomegaly = NPH

6. Differential Diagnosis

1. Alzheimer disease with predominant memory impairment
2. Parkinson disease with rigidity and tremor
3. Vascular dementia with stepwise decline
4. Obstructive hydrocephalus with increased intracranial pressure

7. Management

1. Ventriculoperitoneal shunt is the treatment of choice
2. Best outcomes seen in patients with predominant gait disturbance
3. Early intervention improves prognosis

8. Prognosis

1. Gait symptoms improve first and most significantly
2. Cognitive and urinary symptoms improve less predictably

9. Key Clinical Insight

An elderly patient with gait instability, urinary incontinence, and cognitive decline with enlarged ventricles likely has normal pressure hydrocephalus

10. Exam Level Pearls

1. Magnetic gait is the earliest and most prominent feature
2. Normal CSF pressure does not exclude hydrocephalus
3. Ventriculomegaly without cortical atrophy is key imaging finding
4. CSF tap test predicts response to shunting
5. Gait improves more than cognition after treatment

Pneumocystis jirovecii pneumonia (PJP)

A 33 year old male with a known history of HIV infection presents to the emergency department with a 7 day history of progressive shortness of breath, dry cough, and fever. His CD4 count is 90 cells/μL despite being on antiretroviral therapy. On examination, blood pressure is 110/70 mm Hg, pulse rate is 108 beats per minute, respiratory rate is 22 breaths per minute, oxygen saturation is 92% on room air, and temperature is 100.9 F. Lung auscultation reveals bilateral crackles, although examination may be normal in some cases. There is no peripheral edema or lymphadenopathy. Laboratory evaluation shows a normal leukocyte count with lymphopenia. Chest X ray shows diffuse bilateral perihilar interstitial infiltrates, and CT scan demonstrates bilateral ground glass opacities. Arterial blood gas shows respiratory alkalosis with hypoxemia (PaO2 50 mm Hg) and an increased A–a gradient. Bronchoalveolar lavage with silver stain reveals disc shaped cysts. Diagnosis?

Diagnosis is Pneumocystis jirovecii pneumonia.

1. Definition

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic fungal infection that primarily affects immunocompromised patients, especially those with HIV infection with CD4 < 200 cells/μL.

2. Etiology

2.1 Major Risk Factors

1. HIV infection with CD4 < 200 cells/μL
2. Chronic glucocorticoid use
3. Immunosuppressive therapy
4. Hematologic malignancies and organ transplantation

3. Pathophysiology

1. Organism attaches to type I alveolar epithelium
2. Causes host mediated inflammatory response leading to diffuse alveolar damage
3. Results in impaired gas exchange, hypoxemia, and possible respiratory failure

4. Clinical Features

1. Subacute onset over days to weeks in HIV patients
2. Fever, dry cough, and progressive dyspnea
3. Tachypnea, tachycardia, and hypoxemia
4. Lung examination may be normal in up to 50% of cases or show crackles

5. Diagnostic Evaluation

5.1 Imaging

1. Chest X ray shows diffuse bilateral perihilar interstitial infiltrates
2. CT chest shows ground glass opacities, highly sensitive

5.2 Laboratory Findings

1. Elevated LDH
2. Elevated beta D glucan
3. Hypoxemia with increased A–a gradient

5.3 Microbiological Diagnosis

1. Bronchoalveolar lavage or induced sputum
2. Identification by silver stain, PCR, or immunofluorescence

6. Key Diagnostic Insight

HIV with CD4 < 200 + subacute dyspnea + ground glass opacities + hypoxemia = Pneumocystis jirovecii pneumonia

7. Management

7.1 First Line Treatment

1. Trimethoprim sulfamethoxazole (TMP SMX) for 21 days

7.2 Indications for Adjunctive Corticosteroids

1. PaO2 ≤ 70 mm Hg
2. A–a gradient ≥ 35 mm Hg
3. Start within 72 hours in moderate to severe disease

7.3 Additional Measures

1. Initiate or optimize antiretroviral therapy within 2 weeks once stable

8. Prophylaxis

1. TMP SMX prophylaxis in patients with CD4 < 200 cells/μL
2. Also indicated in CD4 < 14% or oropharyngeal candidiasis

9. Complications

1. Respiratory failure
2. Pneumothorax
3. Rare extrapulmonary involvement
4. High mortality in severe disease

10. Key Clinical Insight 

HIV with CD4 < 200 presenting with subacute dyspnea, dry cough, and hypoxemia strongly suggests Pneumocystis jirovecii pneumonia

11. Exam Level Pearls

1. Ground glass opacities are classic
2. Dry cough with hypoxemia is typical
3. Normal lung exam does not exclude disease
4. Steroids reduce mortality in moderate to severe cases
5. TMP SMX is both treatment and prophylaxis

Spontaneous Bacterial Peritonitis (SBP)

A 55 year old male with a history of cirrhosis and ascites due to chronic alcohol use presents to the emergency department with diffuse abdominal pain, vomiting, and low-grade fever for two days. He also reports fatigue and increasing confusion. On examination, blood pressure is 100/60 mm Hg, pulse rate is 108 beats per minute, respiratory rate is 18 breaths per minute, and temperature is 100.2°F. The abdomen is distended with shifting dullness, with diffuse tenderness and hypoactive bowel sounds. Laboratory findings show WBC count 14,000/mm³, serum creatinine 1.8 mg/dL, and serum albumin 2.1 g/dL. Paracentesis reveals ascitic fluid neutrophil count of 380 cells/mm³. Diagnosis?

Diagnosis is Spontaneous Bacterial Peritonitis (SBP).

1. Definition

Spontaneous bacterial peritonitis is an infection of ascitic fluid without an identifiable surgically treatable intra-abdominal source.

2. Etiology

1. Escherichia coli most common
2. Klebsiella species
3. Streptococcus species

3. Pathophysiology

1. Bacterial translocation from the gut
2. Impaired host immunity in cirrhosis
3. Infection of low-protein ascitic fluid

4. Clinical Features

1. Fever
2. Diffuse abdominal pain
3. Altered mental status
4. Hypotension and tachycardia
5. May present with subtle symptoms or clinical deterioration

5. Diagnostic Evaluation

5.1 Ascitic Fluid Analysis

1. Neutrophil count ≥ 250 cells/mm³ is diagnostic
2. Ascitic fluid culture should be obtained

5.2 Laboratory Findings

1. Leukocytosis
2. Elevated creatinine indicating renal dysfunction
3. Low serum albumin

6. Key Diagnostic Insight

Cirrhosis + ascites + neutrophils ≥ 250 cells/mm³ = SBP

7. Complications

1. Hepatorenal syndrome
2. Sepsis
3. Hepatic encephalopathy
4. High mortality if untreated

8. Management

8.1 Antibiotic Therapy

1. Start empiric third-generation cephalosporin such as cefotaxime or ceftriaxone immediately

8.2 Albumin Infusion

1. Intravenous albumin reduces risk of renal failure and mortality
2. Typical dosing: 1.5 g/kg on day 1 and 1 g/kg on day 3

8.3 Secondary Prophylaxis

1. Ciprofloxacin or trimethoprim sulfamethoxazole
2. Indicated in patients with prior SBP or low ascitic protein

9. Key Clinical Insight

SBP should be suspected in any patient with cirrhosis and ascites who develops clinical deterioration, even with minimal abdominal findings

10. Exam Level Pearls

1. Ascitic neutrophils ≥ 250 cells/mm³ is diagnostic
2. E. coli is the most common organism
3. Do not delay antibiotics while awaiting culture results
4. Albumin prevents hepatorenal syndrome
5. Always perform diagnostic paracentesis in cirrhotic patients with ascites and new symptoms