Encephalitis vs Meningitis
Meningitis and encephalitis have similar causes and symptoms. There is a certain degree of brain inflammation in meningitis and a certain degree of meningeal inflammation in encephalitis. However, they are two different conditions. This article will talk about both encephalitis and meningitis in detail, highlighting their clinical features, symptoms, causes, investigation and diagnosis, prognosis, and also the course of treatment they require and the differences between encephalitis and meningitis.
Meningitis is inflammation of the meninges caused by bacteria, viruses, fungi or parasites. Bacterial meningitis is a killer, and it kills quickly. Organisms like E coli, beta hemolytic streptococci, Listeria moncytogenes, Heamophilus, Nisseria meningitidis, pneumococcus, cause meningitis. Meningitis presents with headache which worsens when exposed to light, stiff neck, Kernig’s sign (pain and resistance on passive knee extension with hips fully flexed), Brudzinski sign (hips flex on bending head forward) and opisthotonus. These are known as meningeal features. Meningitis increases pressure inside the skull. This is characterized by headache, irritability, drowsiness, vomiting, fits, papilledema, reduced level of consciousness, irregular respiration, low pulse rate and high blood pressure. (Read Difference Between Pulse Rate and Blood Pressure.) When the organism enters the bloodstream, septic signs like feeling ill, joint swelling, joint pain, odd behavior, rash, diffuse intravascular coagulation, rapid breathing, rapid pulse and low blood pressure occur.
Treatment to meningitis should not be delayed until test results arrive. If meningitis is suspected, nothing should delay intravenous antibiotics. Airway, breathing, and circulation should be maintained. High flow oxygen therapy via a face mask is good. Treatment protocol differs according to the presentation. If septic signs predominate, lumbar puncture should not be attempted. If the patient is in shock, volume resuscitation is indicated. If meningitic features predominate at presentation, lumbar puncture should be attempted if no features of increased intracranial pressure are present. Intravenous antibiotics should be given. If there is any indication of respiratory failure, intubation should not be delayed.
Complications of meningitis are cerebral edema, cranial nerve lesions, deafness, and cerebral venous sinus thrombosis. Lumbar puncture is critical to diagnosis. If there are no features of increased intra cranial pressure, lumbar puncture should be done. If there are features of increased pressure inside the skull, CT should precede lumbar puncture. 3 bottles of cerebrospinal fluid should be sent for gram stain, Zheil neilson stain, cytology, virology, glucose, protein, and culture. Cerbrospinal fluid analysis may be normal early on. If indicated lumbar puncture should be repeated. Other tests like blood culture, blood glucose, full blood count, urea, electrolytes, chest x-ray, urine culture, nasal swab and stools for virology may be indicated.
Risk factors for meningitis are overcrowding, head injury, infective focus, very young, very old, complement deficiency, antibody deficiency, cancers, sickle cell disease, and CSF shunts. Acute bacterial meningitis has a mortality 70 to 100% untreated; Neisseria meningitides has an overall mortality of 15%, in the west. Survivors are at risk of permanent neurological deficits, mental retardation, sensorineural deafness and cranial nerve palsies.
Encephalitis is inflammation of the brain parenchyma. Viruses like herpes simplex, Japanese encephalitis virus, coxackie, echovirus, HIV, rabies and West Nile, bacteria like staphylococcus are some of the known causative agents. Measels virus causes a subacute sclerosing panencephalitis.
Patients present with meningitis features, fits, coma, reduced level of consciousness and psychiatric features. Unreliable clinical signs, poor immunity and less prominent meningism point towards the diagnosis. Investigations for encephalitis are the same as for meningitis. If treatment is delayed encephalitis kills quickly.
What is the difference between Encephalitis and Meningitis?
• Meningitis is inflammation of the meninges while encephalitis is inflammation of the brain parenchyma.
• Meningitis presents with prominent meningism while, in encephalitis, meningism is less prominent.
• Clinical differentiation is by identifying relative involvement of the brain and the meninges.
• Investigations for encephalitis and meningitis are the same.
• Both encephalitis and bacterial meningitis are killer diseases; treatment should not be delayed as both kill quickly.