Neuro

Neurological Conditions

Seizure Disorder

  • Definition: A prevalent neurological condition characterized by abnormal electrical activity in the brain.

  • Chronic condition also known as Epilepsy. It refers to having two or more unprovoked seizures.

Inflammatory/Infectious Disorders

Meningitis

  • Definition: Inflammation of the meningeal tissues in the brain and spinal cord.

  • Etiology: Caused by infections (e.g., from the lungs or bloodstream) or penetrating wounds.

  • Major bacteria responsible for meningitis include:
       - Streptococcus pneumoniae
       - Neisseria meningitidis (bacterial)
       - Enteroviruses (viral)

Encephalitis

  • Definition: Acute inflammation of the brain.

  • Etiology: Primarily viral infections.
       - Notable viruses include:
         - West Nile virus (transmitted via mosquitoes)
         - Measles, chicken pox, mumps
         - Herpes simplex virus-1 (HSV)

Terminology

Seizure

  • Defined as a brief episode of abnormal electrical activity in the nerve cells of the brain cortex.

  • Characteristics:
      - It can involve:
        - Motor manifestations (e.g., convulsions)
        - Cognitive manifestations
        - Sensory manifestations

Seizure Disorder (Epilepsy)

  • Definition: A chronic condition marked by recurrent unprovoked seizures.

  • Key aspects:
      - No metabolic causes detected during seizures.
      - Changes in electroencephalographic (EEG) recordings, revealing unorganized electrical activity.

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

Seizure Etiology

Primary (Idiopathic)

  • Seizures with no identifiable cause.

Secondary Causes

  • Factors contributing to seizure onset include:
      - Brain Injury: Trauma causing bleeding on the brain.
      - Stroke: Reduced oxygen supply to the brain.
      - Toxic and Electrolyte Imbalances: Low blood sugar, sodium, and calcium levels.
      - Medications: Influence from drugs can provoke seizures.

Secondary Etiology by Age Groups

  1. Children:
       - Birth trauma leading to low oxygen.
       - Infections such as meningitis.
       - Congenital abnormalities.
       - Febrile seizures due to rapid-onset high fevers.

  2. Middle Age:
       - Head trauma, infections, alcohol use, stimulants, and medications.

  3. Elderly:
       - Presence of brain tumors and strokes.

Seizure Pathogenesis

Seizure Focus

  • Defined as a group of abnormal neurons that spontaneously generate electrical impulses.

  • This focus is typically associated with scar tissue (gliosis).

Characteristics

  • Functions autonomously, emitting excessive paroxysmal electrical discharges.

  • Can recruit nearby neurons to discharge aberrantly, leading to a spread of electrical activity locally or globally.

Seizure Threshold

Factors Lowering Seizure Threshold

  • Common factors include:
      - Sleep deprivation

  • Occasional factors include:
      - Barbiturate and alcohol withdrawal
      - Epileptogenic drugs
      - Televisions flickering
      - Systemic infections
      - Head trauma
      - Recreational drug use
      - Non-compliance with Antiepileptic Drug (AED) treatments
      - Menstruation
      - Dehydration
      - Hyperventilation
      - Flashing lights
      - Diet and missed meals
      - Specific reflex triggers (e.g., stress and intense exercise).

Types of Seizure Thresholds

  1. Non-epileptic seizure threshold

  2. Epileptic seizure threshold

Electroencephalography (EEG)

  • EEG is a critical tool in the diagnosis and classification of seizures. Types highlighted are:
      - Normal
      - Partial seizure
      - Generalized seizure

Clinical Manifestations of Seizures

  • Dependent on the location of the seizure focus.

  • May include a combination of:
      - Sensations and perceptions
      - Muscle movements
      - Altered consciousness

Seizure Classification

Types of Seizures

  1. Focal/Partial Seizures:
       - Caused by localized irritations in the brain.
       - Can be unilateral or may progress to generalized seizures.

  2. Generalized Seizures:
       - Involves both hemispheres of the brain.
       - Includes:
         - Tonic-Clonic Seizures (also known as Grand Mal)
         - Absence Seizures
         - Partial Seizures (Simple & Complex)
           - Partial seizures can evolve into generalized seizures.

Detailed Characteristics
Generalized Tonic-Clonic Seizure

  • Also known as Grand Mal seizure.

  • Key features include:
      - Salivation and tongue biting.
      - Incontinence (loss of control over bladder/bowel).
      - No recollection of the event (loss of memory).

  • Stages:
      - Tonic Phase: Stiffening of the body lasting 10-20 seconds.
      - Clonic Phase: Jerking movements of the extremities lasting 30-40 seconds.

Generalized Absence Seizure

  • Also termed Petit Mal seizure.

  • Primarily occurs in children and generally outgrown by adolescence.

  • Characteristics include brief episodes of:
      - Staring spells
      - Extremely short loss of consciousness (may happen multiple times per day, up to 100 times a day).

Partial Seizures

  1. Simple Partial Seizures:
       - No loss of consciousness.
       - Duration: Less than 1 minute.
       - Can involve motor, sensory, or other phenotypes.

  2. Complex Partial Seizures:
       - Typically originating from the temporal lobe. Key aspects include:
         - Alteration in consciousness.
         - Lasts usually between 45-90 seconds.
         - Begins motionless with a fixed gaze and may follow with automatism (repetitive, purposeless movements).
         - Concludes with a brief period of confusion.

Phases of Seizures

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

  2. Aural Phase: Sensory warnings prior to the seizure.

  3. Ictal Phase: The actual seizure.

  4. Postictal Phase: Recovery following the seizure.

Aura/Prodromal Phase Characteristics

  • Describes the subjective experience before a seizure, often recognized as a clue to the seizure focus.

  • Symptoms may include:
      - Jerking movements
      - Headaches
      - Fatigue
      - Mood alterations
      - Sensory experiences (specific smells, tastes, sounds).

Postictal Phase

  • Varies per individual, lasting seconds to days.

  • Duration depends on:
      - Severity of seizure
      - Brain area affected
      - Seizure frequency.

  • Common symptoms include muscle fatigue and lethargy.

Status Epilepticus

  • Definition: A continuous seizure lasting longer than 15 minutes or repeated seizures without regaining consciousness.

  • A medical emergency due to risks:
      - Cardiac and respiratory dysfunction.
      - Potential for permanent neurological injury or death (also associated with hyperthermia).

Pharmacotherapy of Seizure Disorder

Antiepileptic Drugs (AEDs)

Goals of AED Therapy

  • Raise the seizure threshold and reduce the frequency of seizures.

  • Enable patients to live normal or nearly normal lives.

  • Usually prescribed for long-term treatment while balancing effectiveness with side effects.

Mechanisms of Action of AEDs

  1. Suppression of Sodium Influx (blocking sodium channel activity).

  2. Suppression of Calcium Influx: Inhibit channels allowing calcium into cells.

  3. Blocking Glutamate Receptors: Targets the excitatory neurotransmitter glutamate.

  4. Potentiation of GABA: Enhances the effect of the inhibitory neurotransmitter GABA.
       - Enhances GABA receptor activity and promotes its release, suppressing seizure activities.

Traditional AEDs

  • Typical examples include:
      - Phenytoin (Dilantin): Highly utilized, works by inhibiting hyperactive sodium channels.
      - Valproic Acid (Depacon)
      - Carbamazepine (Tegretol)
      - Phenobarbital (Solfoton)
      - Ethosuximide (Zarontin)

  • Notable characteristics:
      - Established efficacy with extensive clinical expertise.
      - Various side effects; poor tolerance in some patients.

Newer AEDs

  • Examples include:
      - Gabapentin (Neurontin): GABA potentiator.
      - Pregabalin (Lyrica)
      - Felbamate (Felbatol)
      - Topiramate (Topamax)

  • Highlights:
      - Established efficacy with less clinical experience compared to traditional drugs.
      - Considered safer in pregnancy and typically more expensive.

Drug Specific Information
Phenytoin (Dilantin)

  • Therapeutic range for effective management is critical.
      - Therapeutic Window: Concentration range where it is effective without toxicity.
      - Plasma concentration levels must be monitored:
        - 0.5 mg/L: No therapeutic effect.
        - 5-10 mg/L: Mild anti-convulsant action.
        - 10-20 mg/L: Optimal for anticonvulsant effect.
        - 20-30 mg/L: Nystagmus and blurred vision.
        - 30 mg/L: Risk of ataxia, drowsiness, coma.

Adverse Effects of AEDs

  • Central Nervous System Depression: Includes symptoms like drowsiness, fatigue, sedation, confusion.

  • Children may exhibit hyperactivity and sleep disorders.

  • Possible GI disturbances and motor disturbances like abnormal movements (e.g., muscle spasms).

Phenytoin Specifics

  • Noteworthy adverse effects include:
      - Gingival hyperplasia
      - Acne and hirsutism
      - Hypertrophy of facial tissue

Drug Interactions and Considerations

  • Phenytoin is a cytochrome P450 inducer.
      - Impacts medications metabolized by this pathway (increased drug clearance).
      - Careful monitoring is essential with concurrent administration of other CYP450 substrates (e.g., oral contraceptives) to prevent elevated toxicity or reduced effectiveness.

Meningitis

Symptoms and Risk Factors

Classic Triad of Symptoms

  1. Fever

  2. Headache

  3. Stiff Neck

Risk Factors

  • Primarily affects older adults, college students, and prisoners.

  • Vaccination campaigns have notably decreased the incidence of certain types (e.g., N. Meningitides).

Pathogenesis

  • Infection mainly targets the arachnoid mater and cerebrospinal fluid (CSF), leading to an inflammatory response and pus secretion.

  • Resulting symptoms include contribution to increased intracranial pressure (ICP).

Treatment Options for Meningitis

Bacterial Meningitis Treatment

  • Immediate aggressive antibiotic therapy is critical until CSF analysis returns.

  • Broad-spectrum intravenous antibiotics may include:
      - Ceftriaxone (Rocephin)
      - Vancomycin
      - Acyclovir

  • Additionally, steroid therapy may be indicated.

  • Prophylactic vaccination is important against:
      - Meningococcus
      - Pneumococcus
      - H. influenzae

Encephalitis

Clinical Manifestations

  • Signs typically emerge on day 2 or 3 following the infection, presenting symptoms ranging from mild cognitive alterations to coma.

  • Common symptoms:
      - Fever, headache, nausea/vomiting, seizures, dizziness, and unstable gait.

Encephalitis Pharmacotherapy

  • Acyclovir is the primary drug used for HSV infections, reducing mortality risk but does not mitigate neurological complications.

Brain Abscess

Definition

  • A localized accumulation of pus within brain tissue, often consequent of local or systemic infections (frequently stemming from ear, tooth, or sinus infections).

  • Common causative organisms include Streptococci and Staphylococcus aureus.

Symptoms and Signs

  • Presenting symptoms are similar to meningitis: headache, fever, nausea/vomiting.

  • Focal symptoms may manifest depending on the abscess's location in the brain, including:
      - Example: Temporal lobe abscess may lead to visual field defects.

Final Note

  • Be aware of the neurological implications of seizures, meningitis, encephalitis, and brain abscesses, including both immediate and long-term consequences resulting from these conditions.