Neuro

Neurological Conditions Overview

Neurological conditions encompass a variety of disorders affecting the brain, spinal cord, and nerves. This guide covers:

  • Seizure Disorder

  • Inflammatory/Infectious Disorders

    • Meningitis

    • Encephalitis

Seizure Disorder

Seizure Terminology:

  • Seizure: A brief episode characterized by abnormal electrical activity in the brain's nerve cells, with potential manifestations affecting motor, cognitive, or sensory functions.

  • Seizure Disorder (Epilepsy): Defined as chronic, recurrent seizures characterized by two or more unprovoked episodes.

Brain and Seizures

The brain is described as a "picky organ" needing a perfect balance of various factors. Any imbalance can lead to seizures.

Seizure Etiology

Primary vs. Secondary Causes:

  • Primary (Idiopathic): No identifiable cause.

  • Secondary: Caused by identifiable factors such as:

    • Brain injury (traumatic, causing bleeding)

    • Stroke (causing low oxygen)

    • Toxic imbalances (electrolyte imbalances)

    • Medication effects

    • Metabolic issues (low sugar, sodium, calcium)

Secondary Etiology by Age Groups:

  • Children:

    • Birth trauma (low oxygen)

    • Infections (Meningitis)

    • Congenital abnormalities

    • Rapid-onset high fevers (febrile seizures)

  • Middle Age:

    • Head trauma

    • Infections (Meningitis)

    • Alcohol and stimulant impacts

  • Elderly:

    • Brain tumors

    • Strokes

Seizure Disorder (Epilepsy)

  • Definition: Recurrent, unprovoked seizures without identifiable metabolic causes.

  • EEG Changes: May present as unorganized electrical activity resembling an electrical storm in the brain.

  • Prevalence: Affects approximately 0.5% of the U.S. population.

Seizures: Pathogenesis

Seizure Focus:

  • A group of abnormal neurons that fire spontaneously. Often associated with gliosis (scar tissue in brain).

  • Functions autonomously, emitting excessive electrical discharges that can spread locally (remaining focal) or globally throughout the brain.

Seizure Threshold Factors

Common Factors Lowering Seizure Threshold:

  • Common Triggers: Sleep deprivation

  • Occasional Triggers:

    • Barbiturate withdrawal

    • Alcohol withdrawal

    • Television flicker

    • Epileptogenic drugs

    • Systemic infection

    • Head trauma

    • Recreational drugs

    • Antiepileptic drug (AED) non-compliance

    • Menstruation

    • Dehydration

    • Benzodiazepine withdrawal

    • Hyperventilation

    • Flashing lights

    • Missed meals and specific reflex triggers

    • Stress

    • Intense exercise

Electroencephalographic Monitoring

  • EEG: Stands for electroencephalogram, an essential tool in diagnosing and understanding seizure activity.

Clinical Manifestations of Seizures

The effects depend on the location of the seizure focus and may encompass:

  • Sensations and perceptions

  • Muscle movements

  • Altered consciousness

Classification of Seizures

Types:

  • Focal/Partial Seizures: Begins from focal irritations, can remain unilateral or become generalized.

  • Generalized Seizures: Affect both sides of the brain.

Specific Types of Seizures:

  • Generalized Seizures:

    • Tonic-Clonic Seizures (Grand Mal): Characterized by loss of consciousness, stiffening (tonic) lasting 10-20 seconds, followed by jerking (clonic) lasting 30-40 seconds, often accompanied by tongue biting and incontinence.

    • Absence Seizures (Petit Mal): Common in children, characterized by brief staring spells with a very short loss of consciousness, can occur several times a day.

  • Partial Seizures:

    • Simple Partial: No loss of consciousness, lasts less than 1 minute, can involve sensory or motor phenomena.

    • Complex Partial: Generally starts in the temporal lobe, includes alterations in consciousness, lasts 45-90 seconds, and follows with repetitive, purposeless movements called "automatism".

Phases of a Seizure

  1. Prodromal Phase: Signs or activity preceding a seizure.

  2. Aural Phase: Sensory warnings experienced before the seizure.

  3. Ictal Phase: The actual seizure itself.

  4. Postictal Phase: Recovery period following the seizure, duration varies depending on severity.

Postictal Phase

Symptoms can last seconds to days, depending on seizure severity and brain area affected, often including muscle fatigue and lethargy after the seizure.

Status Epilepticus

A medical emergency characterized by continuous seizure activity lasting more than 15 minutes, posing risks of cardiac and respiratory dysfunction, neurological injury, or even death.

Pharmacotherapy for Seizure Disorders

Antiepileptic Drugs (AEDs):

Therapeutic Goals:

  • Raise seizure threshold to reduce seizures

  • Allow patients to live a near-normal life, balancing seizure control with adverse effects.

Mechanisms of Action of AEDs:

  1. Suppress Sodium Influx:

    • Involves blocking sodium channels to decrease action potentials, examples include phenytoin, carbamazepine, and valproic acid.

  2. Suppress Calcium Influx: Same principle as sodium suppression but focusing on calcium channels.

  3. Block Glutamate Receptors: Glutamate is an excitatory neurotransmitter. Drugs like felbamate and topiramate block its action.

  4. Potentiation of GABA: GABA is an inhibitory neurotransmitter. Drugs like gabapentin bind to GABA receptors and promote its release to suppress seizure activity.

Traditional AEDs:

  • Phenytoin (Dilantin), Levetiracetam (Keppra), Phenobarbital, Valproic acid, Ethosuximide, Primidone

  • Most have a well-established efficacy but come with numerous side effects and risks during pregnancy.

New AEDs:

  • Gabapentin, Pregabalin, Felbamate, Topiramate

  • Generally found to have less side effects, are safer in pregnancy, and are more expensive.

Monitoring and Compliance:

  • Plasma levels of drugs must be monitored to ensure effective dosing.

  • Patient adherence is crucial; withdrawal can cause seizures.

  • There's also a potential risk for suicidal ideation with some AEDs.

Phenytoin (Dilantin) Specifics

  • Action: Inhibits hyperactive sodium channels, tailoring doses based on serum levels.

  • Indications: Effective for all epilepsy forms except absence seizures.

  • Therapeutic Range:

    • 0.5 mg/L: no effect

    • 5-10 mg/L: some action

    • 10-20 mg/L: optimum concentration

    • 20-30 mg/L: side effects begin

    • Above 30 mg/L: severe toxicity leads to coma.

Adverse Effects of Phenytoin

  • Common issues:

    • Gingival hyperplasia

    • Acne

    • Hirsutism

    • Facial tissue hypertrophy

  • Numerous drug interactions, being a cytochrome P450 inducer.

Meningitis

Definition

Acute inflammation of the meningeal tissues surrounding the brain and spinal cord.

Etiology

  • Causes include infections from lungs or bloodstream, or penetrating wounds.

  • Major bacteria include Streptococcus pneumoniae, Neisseria meningitidis (Bacterial), and Enteroviruses (Viral).

Risk Factors

  • Higher incidence in older adults, college students, and prisoners. Vaccine availability has decreased incidence among certain demographics.

Classic Symptoms (Triad):

  • Fever

  • Headache

  • Stiff neck

Pathogenesis

  • Results from inflammatory response and pus secretion.

  • CSF production increases, raising intracranial pressure (ICP).

Clinical Symptoms

  • Additional symptoms may include nausea, vomiting, photophobia, altered mental status, and, in severe cases, skin rashes or petechiae.

Diagnosis Indicators

  • Kernig Sign: Resistance to leg extension upon examination.

  • Brudzinski Sign: Neck flexion causing simultaneous hip and knee flexion.

Acute Bacterial vs. Viral Meningitis

  • Bacterial meningitis is more severe with higher fatality rates and potential long-term complications; viral meningitis is milder.

Treatment of Bacterial Meningitis

  • Aggressive antibiotic therapy initiated with broad coverage before specific organisms are identified (e.g., Ceftriaxone, Vancomycin). Vaccination for prevention.

Encephalitis

Definition

Acute inflammation of the brain, typically viral in origin.

Common Viral Causes

  • Include West Nile virus, herpes simplex virus, measles, chickenpox, and mumps.

Clinical Manifestations

  • Symptoms emerge by day 2 or 3 post-infection, ranging from mild mental status changes to severe outcomes like coma.

  • Additional symptoms include fever, headache, nausea, vomiting, seizures, and dizziness.

Pharmacotherapy

  • Treatment often involves antiviral medications like acyclovir, useful for HSV infections; AEDs may also be administered for seizure control.

Brain Abscess

Definition

Accumulation of pus within brain tissue, often a result of local or systemic infections.

Common Etiology

  • Most commonly arises from ear, tooth, or sinus infections caused by Streptococci or Staphylococcus aureus.

Clinical Symptoms

  • Symptoms similar to meningitis, which include headache, fever, and nausea or vomiting. Increased ICP symptoms may present as drowsiness, confusion, or seizures.