D115 Unit 3 Videos: Bacterial Meningitis & Neurologic System Alterations
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Western Governors University
D115 Advanced Pathophysiology for the Advanced Practice Nurse
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D115 Unit 3 Videos: Bacterial Meningitis & Neurologic System Alterations
Bacterial Meningitis
What is Bacterial Meningitis?
Bacterial meningitis is the inflammation of the meninges, which are the pia mater and arachnoid mater membranes that encase the brain and spinal cord. This condition can arise from infections by bacteria, viruses, fungi, parasites, toxins, or even noninfectious causes.
Which Pathogens Are Most Common?
The primary bacterial agents causing meningitis include:
| Pathogen | Notes |
|---|---|
| Neisseria meningitidis (meningococcus) | Leading cause in many populations |
| Streptococcus pneumoniae (pneumococcus) | Common with increasing drug resistance |
Who is at Risk?
Populations most vulnerable include:
- Infants younger than 1 year
- Adolescents
- Adults over 40 years old
Settings prone to outbreaks include college dormitories, military bases, and regions in Sub-Saharan Africa.
What Are Predisposing Factors?
Conditions that increase susceptibility are:
- Otitis media or sinusitis
- Pneumonia
- Immunocompromised states
- Post-splenectomy status or sickle cell disease (especially increasing pneumococcal risk)
How is it Transmitted?
Bacterial meningitis spreads through respiratory droplets or saliva, commonly through close contact such as kissing, coughing, sneezing, or sharing food and drinks. Asymptomatic carriers can also transmit the infection.
What Happens in the Body? (Pathophysiology)
Bacteria enter through the respiratory tract or bloodstream, possibly via neurosurgical interventions. They cross the blood-brain barrier, multiply in cerebrospinal fluid (CSF), and release toxins that increase vascular permeability, causing cerebral edema. Obstruction of CSF flow leads to raised intracranial pressure, which can cause brainstem herniation and death.
What Are the Clinical Features?
| Symptom Category | Symptoms |
|---|---|
| Systemic Signs | Fever, chills, tachycardia |
| Meningeal Signs | Severe headache, photophobia, nuchal rigidity, positive Kernig and Brudzinski signs |
| Neurologic Signs | Reduced consciousness, seizures, hemiparesis, confusion, projectile vomiting, papilledema, petechial rash, bulging fontanels (infants), opisthotonic posturing (children) |
How is it Diagnosed?
Diagnosis involves lumbar puncture revealing increased white blood cells in CSF, alongside blood cultures to identify the causative organism.
What is the Treatment?
Empiric intravenous antibiotics should be initiated immediately, followed by adjustment based on culture results. Dexamethasone is recommended in pneumococcal meningitis, supplemented by supportive care.
What Complications Can Occur?
Potential serious outcomes include septic shock, disseminated intravascular coagulation (DIC), purpura fulminans, and multi-organ failure.
How Can It Be Prevented?
Vaccination against meningococcal, pneumococcal, and Haemophilus influenzae type B bacteria plays a critical role in prevention.
Guillain-Barré Syndrome (GBS)
What is Guillain-Barré Syndrome?
GBS is an acute autoimmune condition targeting the peripheral nervous system, leading to demyelination and ascending muscle weakness.
What Causes GBS?
Often, GBS follows infections or immune system activations caused by agents such as Campylobacter jejuni, cytomegalovirus (CMV), Epstein-Barr virus (EBV), influenza, Mycoplasma pneumoniae, and Zika virus. It may also be triggered by surgery or immunization.
What is the Underlying Mechanism?
Molecular mimicry causes antibodies to attack peripheral nerve myelin or axons, and complement activation impairs nerve conduction.
What Are the Subtypes of GBS?
| Subtype | Description |
|---|---|
| Acute inflammatory demyelinating polyneuropathy | Most common variant |
| Acute motor axonal neuropathy | Involves motor nerves |
| Acute motor-sensory axonal neuropathy | Affects both motor and sensory nerves |
| Miller Fisher syndrome | Rare; characterized by ataxia, ophthalmoplegia, and areflexia |
What Symptoms Does GBS Present?
Patients develop ascending flaccid paralysis, paresthesia, muscle weakness, areflexia, autonomic instability, and may progress to respiratory muscle paralysis within two weeks.
How is GBS Diagnosed?
The diagnosis requires progressive weakness in at least two limbs, areflexia, and symptom progression over less than four weeks.
What Treatment Options Exist?
Treatment includes intravenous immunoglobulin (IVIG), plasmapheresis, and aggressive rehabilitation.
What is the Prognosis?
Recovery may span weeks to months, sometimes up to two years, with approximately 30% of patients experiencing residual weakness.
Multiple Sclerosis (MS)
What Defines Multiple Sclerosis?
MS is a chronic autoimmune disorder characterized by demyelination in the central nervous system (CNS).
What is the Pathophysiology?
Activated T-cells penetrate the blood-brain barrier, releasing cytokines that damage oligodendrocytes. This results in demyelinated plaques visible on MRI. While early remyelination occurs, it diminishes over time.
Who is at Risk?
Risk factors include:
- Female gender
- Presence of HLA-DR2 gene
- Vitamin D deficiency
- Living farther from the equator
What Types of MS Exist?
| Type | Description |
|---|---|
| Relapsing-remitting | Most common form, characterized by flare-ups and remissions |
| Secondary progressive | Initially relapsing-remitting, then steadily worsening |
| Primary progressive | Continuous worsening from onset |
| Progressive-relapsing | Steady decline with acute relapses |
What Are Common Symptoms?
Between ages 20 and 40, patients commonly experience motor symptoms (weakness, tremor, spasticity, ataxia), sensory changes (numbness, paresthesia), visual disturbances (optic neuritis, diplopia), speech difficulties (dysarthria), autonomic dysfunction, and cognitive issues including depression and impaired concentration. Charcot’s triad of dysarthria, nystagmus, and intention tremor is a hallmark.
How is MS Diagnosed?
Diagnosis is based on MRI showing CNS plaques, CSF analysis revealing oligoclonal bands, visual evoked potentials, and clinical evidence of symptoms separated in time and space.
What Treatments Are Available?
Acute exacerbations are managed with corticosteroids, IVIG, or plasmapheresis. Disease-modifying therapies include interferon-beta and immunosuppressants. Rehabilitation addresses symptoms and functional impairment.
Myasthenia Gravis
What is Myasthenia Gravis?
A chronic autoimmune disorder leading to fluctuating skeletal muscle weakness due to impaired neuromuscular transmission.
What Causes It?
Autoantibodies target and destroy acetylcholine receptors at the neuromuscular junction, disrupting communication between nerves and muscles.
What Symptoms Are Characteristic?
Typical signs include ptosis, diplopia, facial weakness, difficulty chewing, swallowing, and speaking, limb and neck weakness, with symptoms improving after rest.
How is Diagnosis Made?
| Diagnostic Tool | Purpose |
|---|---|
| Acetylcholine receptor antibodies | Detect autoantibodies |
| Anti-MuSK antibodies | Alternative antibody detection |
| Electromyography (EMG) | Assess neuromuscular transmission |
| Edrophonium test | Temporary symptom improvement test |
| CT/MRI | Identify thymoma if present |
What Are Treatment Approaches?
Management includes anticholinesterase medications, immunosuppressants, thymectomy if thymoma is present, and IVIG or plasmapheresis during exacerbations.
Diabetes Mellitus
Overview
Diabetes Mellitus is a metabolic disease marked by chronic high blood glucose levels due to either insufficient insulin production or resistance to insulin action.
How Is Blood Sugar Regulated?
Insulin lowers blood glucose, whereas glucagon raises it. Both hormones are produced in pancreatic islets.
Type 1 Diabetes Mellitus
- Caused by autoimmune destruction of pancreatic β-cells, leading to absolute insulin deficiency.
- Linked to HLA-DR3 and DR4 genotypes.
- Presents with classic symptoms: polyphagia, polyuria, polydipsia, and glycosuria.
- Complication includes diabetic ketoacidosis (DKA).
- Requires lifelong insulin therapy.
Type 2 Diabetes Mellitus
- Characterized by insulin resistance and relative insulin deficiency.
- Strongly associated with obesity and genetic predisposition.
- Complication includes hyperosmolar hyperglycemic state (HHS).
- Treatment emphasizes lifestyle changes, oral antidiabetic drugs like metformin, and insulin if necessary.
How is Diabetes Diagnosed? (WHO Criteria)
| Test | Diagnostic Threshold |
|---|---|
| Fasting glucose | ≥126 mg/dL |
| Random glucose | ≥200 mg/dL |
| Oral glucose tolerance test (OGTT) | ≥200 mg/dL at 2 hours |
| HbA1c | ≥6.5% |
Hyperparathyroidism
What is Hyperparathyroidism?
It is characterized by excessive secretion of parathyroid hormone (PTH), causing elevated calcium levels in the blood.
What Are the Types?
| Type | Cause |
|---|---|
| Primary | Parathyroid adenoma or hyperplasia |
| Secondary | Chronic hypocalcemia from chronic kidney disease or vitamin D deficiency |
| Tertiary | Autonomous PTH secretion after prolonged secondary hyperparathyroidism |
What Symptoms Occur?
Common manifestations include kidney stones, bone pain, fractures, osteoporosis, gastrointestinal disturbances (constipation, nausea), neuropsychiatric symptoms, polyuria, and polydipsia.
How Is It Managed?
Primary hyperparathyroidism is treated surgically. Secondary hyperparathyroidism involves managing vitamin D and phosphate levels, and medications like calcimimetics (e.g., cinacalcet).
Thyroid Disorders
Hyperthyroidism (Graves’ Disease)
- Caused by autoimmune stimulation of TSH receptors.
- Symptoms include weight loss, tremor, anxiety, and heat intolerance.
- Laboratory findings show decreased TSH and increased T3/T4.
- Treatment includes antithyroid drugs, beta-blockers, and surgery.
- Thyroid storm is a life-threatening exacerbation requiring ICU care.
Hypothyroidism (Hashimoto’s Thyroiditis)
- Autoimmune destruction of the thyroid gland.
- Presents with fatigue, weight gain, and cold intolerance.
- Treated with levothyroxine replacement therapy.
Otitis Media
What is Otitis Media?
It is inflammation of the middle ear, predominantly affecting children.
How is It Diagnosed?
Diagnosis is based on reduced tympanic membrane mobility, confirmed with tympanometry or pneumatic otoscopy.
What is the Treatment?
High-dose amoxicillin is the first-line treatment. Watchful waiting is recommended for mild cases.
Mental Health Disorders
| Disorder | Definition | Treatment |
|---|---|---|
| Depression | ≥2 weeks of depressed mood or loss of interest | SSRIs, psychotherapy, or combination |
| Generalized Anxiety Disorder (GAD) | Excessive worry lasting ≥6 months | Cognitive behavioral therapy (CBT), SSRIs/SNRIs |
| Schizophrenia | Psychotic disorder with positive, negative, and cognitive symptoms | Antipsychotics and psychosocial therapy |
References
American Diabetes Association. (2023). Classification and diagnosis of diabetes. Diabetes Care, 46(Supplement_1), S19–S33. https://doi.org/10.2337/dc23-S002
Kumar, V., Abbas, A. K., & Aster, J. C. (2020). Robbins Basic Pathology (10th ed.). Elsevier.
Harrison, T. R. (2018). Harrison’s Principles of Internal Medicine (20th ed.). McGraw-Hill Education.
Jameson, J. L., Fauci, A. S., Kasper, D. L., Hauser, S. L., Longo, D. L., & Loscalzo, J. (2018). Harrison’s Manual of Medicine (19th ed.). McGraw-Hill Education.