CENTRAL NERVOUS SYSTEM DISORDERS.

Febrile Seizures

Definition:

Febrile seizures are seizures occurring in children aged 6 months to 5 years, associated with fever (>38°C) without any underlying CNS infection or metabolic disorder.

Types of Febrile Seizures:

1. Simple Febrile Seizure (Most common)
   • Generalized tonic-clonic seizures
   • Lasts <15 minutes
   • No recurrence within 24 hours
   • No postictal neurological deficits
2. Complex Febrile Seizure
   • Focal seizures
   • Lasts >15 minutes
   • Recurs within 24 hours
   • Postictal neurological deficits present

Causes & Risk Factors:

• Viral infections (Most common, e.g., HHV-6, Influenza, Adenovirus)
• Genetic predisposition
• Rapid rise in body temperature

Signs & Symptoms:

• Fever >38°C
• Generalized or focal seizures
• Brief loss of consciousness
• Postictal drowsiness (only in complex seizures)

Complications:

• Risk of recurrence (~30%)
• Risk of developing epilepsy (higher in complex febrile seizures)

Diagnosis:

• Clinical diagnosis (Based on history and absence of CNS infection)
• Lumbar puncture (If meningitis is suspected)
• EEG (Only in complex seizures)

Management:

• Supportive care (Antipyretics, cooling measures)
• Abortive therapy (IV Lorazepam, Diazepam if seizure persists >5 minutes)
• Reassurance to parents (No long-term effects in simple febrile seizures)

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Meningitis

Definition:

Meningitis is inflammation of the meninges, often caused by bacterial or viral infections.

Types:

1. Bacterial Meningitis (Severe, life-threatening)
   • Neonates: Group B Streptococcus, E. coli, Listeria monocytogenes
   • Children: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae
2. Viral Meningitis (Self-limiting, less severe)
   • Enteroviruses (Coxsackie, Echovirus), Mumps virus, HSV

Signs & Symptoms:

• Fever, headache
• Neck stiffness (Nuchal rigidity, Kernig & Brudzinski signs positive in bacterial cases)
• Photophobia, irritability
• Altered mental status (Severe cases may cause coma)

Complications:

• Seizures
• Hearing loss (Common in bacterial meningitis)
• Hydrocephalus, brain abscess

Diagnosis:

• Lumbar puncture (CSF analysis – Bacterial: High WBC, Low glucose, High protein)
• Blood cultures (To identify bacterial pathogen)
• MRI (If complications like abscess suspected)

Management:

• Empirical IV antibiotics (Ceftriaxone + Vancomycin, Ampicillin in neonates)
• Dexamethasone (Reduces inflammation in bacterial meningitis)
• Supportive care (Fluids, Antipyretics, Oxygen therapy)

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Guillain-Barré Syndrome (GBS)

Definition:

Guillain-Barré Syndrome is an autoimmune-mediated acute inflammatory demyelinating polyneuropathy, often triggered by an infection.

Causes & Risk Factors:

• Post-infectious (Most common cause – Campylobacter jejuni)
• Post-vaccination (Rare association with flu vaccine)
• Autoimmune response (Molecular mimicry leading to nerve damage)

Signs & Symptoms:

• Ascending muscle weakness (Starts in legs, progresses upwards)
• Areflexia (Absent deep tendon reflexes)
• Autonomic dysfunction (Tachycardia, BP instability)
• Respiratory failure (In severe cases due to diaphragm involvement)

Complications:

• Respiratory paralysis (Requires ICU support in severe cases)
• Chronic fatigue and muscle weakness (Post-recovery sequelae)

Diagnosis:

• Nerve conduction studies (Slowed conduction velocity in demyelinating GBS)
• CSF analysis (High protein, Normal WBC – “Albuminocytologic dissociation”)

Management:

• IV Immunoglobulin (IVIG) or Plasma exchange (Plasmapheresis)
• Respiratory support (If vital capacity <20 mL/kg)
• Physical therapy for rehabilitation

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Acute Flaccid Myelitis (AFM)

Definition:

AFM is a rare polio-like neurological disorder, causing sudden muscle weakness and paralysis in children.

Causes:

• Enterovirus D68 (Most common viral cause)
• West Nile virus, Poliovirus (Rare in vaccinated populations)

Signs & Symptoms:

• Acute limb weakness (Asymmetrical, sudden onset)
• Facial and bulbar weakness (Drooping eyelids, slurred speech, difficulty swallowing)
• Hyporeflexia (Absent deep tendon reflexes)

Complications:

• Respiratory muscle paralysis (Requires mechanical ventilation in severe cases)
• Permanent limb weakness or disability

Diagnosis:

• MRI spine (Detects gray matter lesions in spinal cord, distinguishing from GBS)
• CSF analysis (Mild pleocytosis, normal glucose)

Management:

• Supportive care (Physical therapy, Respiratory support if needed)
• Corticosteroids (May reduce inflammation in severe cases)

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Reye’s Syndrome

Definition:

Reye’s syndrome is a rare but life-threatening disorder causing acute encephalopathy and liver failure, typically following viral infections treated with aspirin.

Causes & Risk Factors:

• Aspirin use in viral infections (Influenza, Varicella-Zoster virus)
• Mitochondrial dysfunction affecting liver metabolism

Signs & Symptoms:

• Persistent vomiting
• Altered mental status (Lethargy, confusion, seizures)
• Hepatomegaly (Without jaundice)
• Raised intracranial pressure (Papilledema, Coma in severe cases)

Complications:

• Cerebral edema → Brain herniation
• Liver failure (Elevated AST, ALT, Ammonia levels)

Diagnosis:

• Liver function tests (Elevated AST, ALT, Ammonia, Normal Bilirubin)
• CSF analysis (Normal WBC, Protein, Glucose – To differentiate from meningitis)

Management:

• Supportive care (IV fluids, Electrolyte balance)
• Mannitol (For raised intracranial pressure)
• Avoid aspirin in viral infections (Use acetaminophen instead)

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Key Points for Competitive Exams

✔️ Most common CNS infection in children? – Meningitis (Bacterial/Viral)
✔️ Most common bacterial cause of neonatal meningitis? – Group B Streptococcus
✔️ Best initial test for febrile seizures? – Clinical diagnosis (No need for EEG in simple febrile seizures)
✔️ Classic CSF finding in Guillain-Barré Syndrome? – Albuminocytologic dissociation (High protein, Normal WBC)
✔️ MRI finding in Acute Flaccid Myelitis? – Gray matter involvement in spinal cord
✔️ Most common viral cause of Reye’s Syndrome? – Influenza, Varicella-Zoster virus
✔️ Best treatment for Guillain-Barré Syndrome? – IVIG or Plasmapheresis

Encephalitis

Definition:

Encephalitis is inflammation of the brain parenchyma, usually caused by viral infections, leading to altered mental status, seizures, and neurological deficits.

Causes & Risk Factors:

• Viral infections (Most common cause)
  • Herpes Simplex Virus (HSV-1, HSV-2) (Most severe form)
  • Enteroviruses (Coxsackie, Echovirus)
  • Arboviruses (West Nile, Japanese Encephalitis, Dengue, Zika)
  • Rabies Virus (Bite from infected animals)
• Post-infectious (Autoimmune-mediated) – Acute Disseminated Encephalomyelitis (ADEM)
• Bacterial, fungal, parasitic infections (Less common but severe)

Signs & Symptoms:

• Fever, headache
• Altered mental status (Confusion, disorientation, drowsiness, coma in severe cases)
• Seizures (Common in HSV encephalitis)
• Focal neurological deficits (Hemiparesis, Aphasia, Ataxia)
• Photophobia, neck stiffness (If associated with meningitis – Meningoencephalitis)

Complications:

• Severe brain edema → Brain herniation
• Seizures → Status epilepticus
• Long-term neurological deficits (Cognitive impairment, Speech & Motor dysfunction)

Diagnosis:

• Lumbar puncture (CSF analysis):
  • Viral Encephalitis: Normal glucose, Elevated WBCs, Elevated protein
  • Bacterial Encephalitis: Low glucose, High WBCs, High protein
• MRI Brain (Best imaging test):
  • Temporal lobe involvement → Suggestive of HSV encephalitis
  • Diffuse white matter lesions → Autoimmune encephalitis (ADEM)
• EEG: Generalized slow waves, Seizure activity in focal cases
• CSF PCR (For HSV, Enterovirus, Arboviruses, Rabies, etc.)

Management:

• Empirical IV Acyclovir (For suspected HSV Encephalitis, given until PCR results confirm/deny HSV)
• Supportive therapy (Fever control, Fluids, Electrolytes, Seizure management)
• Corticosteroids (For autoimmune encephalitis/ADEM)
• Rabies Immunoglobulin + Vaccine (For suspected Rabies exposure)

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Pediatric Traumatic Brain Injury (TBI)

Definition:

Traumatic Brain Injury (TBI) is damage to the brain caused by external mechanical force, leading to temporary or permanent neurological dysfunction.

Types of Brain Injury:

1. Primary Injury (Immediate damage at the time of impact)
   • Skull Fractures: Linear, Depressed, Basilar fractures
   • Cerebral Contusions & Lacerations
   • Diffuse Axonal Injury (DAI) (Severe shearing injury leading to coma)
2. Secondary Injury (Delayed brain damage due to ongoing pathophysiology)
   • Brain Edema & Increased Intracranial Pressure (ICP)
   • Hypoxia & Ischemia
   • Seizures, Infections, Hydrocephalus

Causes & Risk Factors:

• Falls (Most common in infants & toddlers)
• Motor vehicle accidents (MVA) (Common in older children, adolescents)
• Non-Accidental Trauma (Shaken Baby Syndrome)
• Sports-related head injuries

Signs & Symptoms:

• Mild TBI (Concussion):
  • Transient loss of consciousness (<30 min)
  • Headache, Nausea/Vomiting
  • Confusion, Amnesia
  • Normal neurological examination
• Moderate to Severe TBI:
  • Prolonged loss of consciousness (>30 min or coma in severe cases)
  • Altered Glasgow Coma Scale (GCS <13)
  • Seizures, Focal neurological deficits
  • Signs of increased ICP (Bradycardia, Hypertension, Irregular breathing – Cushing’s triad)

Complications:

• Epidural Hematoma:
  • Rupture of Middle Meningeal Artery (MMA)
  • Lucid interval followed by rapid deterioration
  • CT Scan: Biconvex (Lentiform) hyperdense collection
• Subdural Hematoma:
  • Tearing of bridging veins
  • Common in shaken baby syndrome
  • CT Scan: Crescent-shaped hyperdense collection
• Post-Traumatic Epilepsy (Common in severe TBI)
• Hydrocephalus (Obstructive type)

Diagnosis:

• Glasgow Coma Scale (GCS) (Best tool for severity assessment)
• CT Brain (First-line in moderate/severe TBI, identifies hemorrhage, fractures, midline shift)
• MRI Brain (Better for detecting Diffuse Axonal Injury and Brainstem injuries)

Management:

• Mild TBI (Concussion):
  • Observation for 24 hours
  • Avoidance of physical activities (Brain rest)
  • Symptomatic management (Analgesics for headache, Antiemetics)
• Moderate to Severe TBI:
  • Airway protection & Oxygenation (Intubation if GCS <8)
  • IV Mannitol or Hypertonic Saline (To reduce ICP)
  • Seizure prophylaxis (IV Phenytoin or Levetiracetam)
  • Surgical decompression (If large hematoma or brain swelling)

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Key Points for Competitive Exams

✔️ Most common cause of encephalitis worldwide? – Viral (HSV-1 most common in developed countries, Japanese Encephalitis in endemic regions)
✔️ CSF finding in viral encephalitis? – Normal glucose, High protein, Elevated WBCs
✔️ Classic MRI finding in HSV encephalitis? – Temporal lobe involvement
✔️ Most common cause of post-infectious encephalopathy? – Acute Disseminated Encephalomyelitis (ADEM)
✔️ Most common cause of pediatric traumatic brain injury (TBI)? – Falls (In infants & toddlers)
✔️ Sign of increasing intracranial pressure (ICP)? – Cushing’s Triad (Hypertension, Bradycardia, Irregular breathing)
✔️ Hematoma with a “lucid interval”? – Epidural Hematoma
✔️ Best initial imaging for head trauma? – CT Brain (Faster than MRI for detecting hemorrhage, fractures)
✔️ Best treatment for increased ICP? – IV Mannitol, Hypertonic Saline, Elevation of Head-of-Bed
✔️ Sign of Diffuse Axonal Injury (DAI) on MRI? – Multiple small hemorrhages in white matter