Causes of Viral Encephalitis

In this article, we will discuss various Causes of Viral Encephalitis. So, let’s get started.

Viral invasion and inflammation of the brain parenchyma is called viral encephalitis. It is an acute febrile illness with some evidence of meningeal involvement and signs and symptoms of diffuse and/or focal brain substance involvement. Some patients have involvement of meninges and brain parenchyma called meningoencephalitis. If the spinal cord is involved, then it is termed encephalomyelitis. It is far more serious than viral meningitis. Following are the various causes of viral encephalitis:


A. Immunocompetent individuals

  • Common
  • Arboviruses (Japanese, St. Louis, Western Equine, California, and WNV)
  • Herpes simplex virus HSV-I and HSV-II
  • Mumps
  • Less Common
  • Cytomegalovirus (CMV)
  • Epstein-Barr virus (EBV)
  • Human immunodeficiency virus (HIV)
  • Measles virus
  • Rare
  • Adenovirus
  • Influenza and Parainfluenza virus
  • Lymphocytic choriomeningitis virus (LCMV)
  • Rabies, rubella

B. Immunocompromised individuals, e.g. HSV, VZV, CMV, EBV, human herpes virus-6.




Common Causes of Coma

In this article, we will discuss some of the Common Causes of Coma. So, let’s get started.


A. Brainstem and Cerebellar lesions

  • Infarction, hemorrhage of brainstem and cerebellum
  • Tumor, trauma
B. Lesions of cerebral hemisphere with edema and brainstem compression
  • Infarction, hemorrhage
  • Encephalitis, meningitis, brain abscess
  • Tumor, trauma (subdural, extradural)
  • Hydrocephalus
  • Hypertensive encephalopathy
  • Status epilepticus
  • Cerebral malaria
C. Metabolic abnormalities
  • Diabetic and hypoglycemic coma
  • Hepatic failure, renal failure, cardiac failure, respiratory failure
  • Severe hyponatremia or hypokalemia
  • Hyper and hypocalcaemia
  • Hypoxia
  • Myxoedema coma, hypopituitarism
  • Adrenal crisis
  • Vitamin deficiencies (e.g. B1, nicotinic acid, B12)
D. Drugs and physical agents
  • Anaesthetic agents
  • Drug overdose or poisoning and alcohol ingestion
  • Hyper and hypothermia
E. Psychogenic/hysteria

Definition of Dengue Hemorrhagic Fever

In this article, we will discuss the Definition of Dengue Hemorrhagic Fever. So, let’s get started.


Dengue hemorrhagic fever is characterized by all manifestations of classical dengue fever, thrombocytopenia, vascular instability, and increased permeability resulting in leakage of intravascular fluid to interstitial space (hemoconcentration) and local hemorrhage (positive tourniquet test, spontaneous petechiae, and/or purpura) or frank hemorrhage (epistaxis, gum bleeding, bleeding into GI tract, i.e. melena or hematochezia) have been described. The hemorrhage is inconstant and is thought to be a combined effect of vascular damage and thrombocytopenia.

As the plasma leakage increases, patient may become restless, irritable, and develops hypotension and shock (cold extremities) called dengue shock syndrome (DSS). In severe cases, frank shock is present with low pulse pressure (<20 mmHg), cyanosis, hepatomegaly, pleural effusion, and ascites. In some cases, severe ecchymosis and GI bleeding may be seen.

Pathogenesis and Pathophysiology of Acute Syncope

In this article, we will discuss the Pathogenesis and Pathophysiology of Acute Syncope. So, let’s get started.

Pathogenesis and Pathophysiology

Syncope results from transient ischemia of the brain usually in upright stature, brought about by reduction in cardiac output or hypotension due to any underlying cause. Depending upon the pathophysiologic mechanisms, syncope may be naturally mediated syncope (vasovagal, neurocardiogenic), postural (orthostatic), and cardiac. The underlying mechanisms in syncope are:

I. Inadequate vasoconstrictive response, examples are vasodepressor, postural syncope.

II. Reduced venous return, i.e. cough, micturition, defecation syncope.

III. Reduced cardiac output, i.e. myocardial and pericardial diseases, obstructive valvular lesions, and arrhythmia.

IV. Altered state of blood, e.g. anemia, hypoxia, hypoxemia etc.

Causes of Atrial Fibrillation

In this article, we will discuss various Causes of Atrial Fibrillation. So, let’s get started.

It is characterized by rapid atrial rate >350 beats/min, uncoordinated atrial contractions and irregular rapid ventricular response. It is a common supraventricular arrhythmia which may occur in paroxysms (paroxysmal atrial fibrillation) and persistent forms (chronic atrial fibrillation). Following are the various causes of atrial fibrillation.


Rheumatic Heart Disease (Mitral Stenosis, Mitral Regurgitation, etc)

Mitral valve prolapse

Hypertensive heart disease

Cardiomyopathy, alcohol induced (holiday heart syndrome)


Congenital heart disease (ASD, Ebstein’s anomaly)

Constrictive pericarditis

Cor pulmonale

Left atrial myxoma

Idiopathic (lone atrial fibrillation)