Diplomate American Board of Internal Medicine

Meningitis Encephalitis Dr.Nusrum Iqbal Diplomate American Board of Internal Medicine Meningitis • Inflammation of the meninges • Micro-organism reach the the meninges – Direct extension (from the ears, nasopharynx, cranial injury) – Blood stream

Immunocompromised patients (HIV and those taking cytotoxic drugs) are at increased risk of meningeal infection by unusual organisms

Causes • Bacteria • Viruses • Fungi • Other organisms • Malignant cells • Drugs and contrast media • Blood following SAH Bacteria • Neiseria meningitidis • streptococcus pneumoniae • staphylococcus aureus • listeria moncytogenes • gram-negative tuberculosis • treponema pallidum Viruses • Enteroviruses – Echo – coxsackie – polio • Mumps • herpes simplex • HIV • epstein-Barr virus Fungi • Cryptococcus neoformans • candida Pathology • In acute bacterial meningitis, the pia-archnoid is congested with polymorphs. A layer of pus forms that may organize to form adhesions, causing cranial nerve palsies and hydrocephalus • In chronic infection (e.g. TB), the brain is covered in a viscous greyish green exudate with numerous meningeal tubercles. Pathology • Adhesions are typically seen. Cerebral edema is common in any bacterial meningitis • In viral meningitis there is a predominantly lymphocytic inflammatory reaction in the CSF without pus formation or adhesion Clinical Features • The meningitic syndrome – headache – neck stiffness and fever – photophobia – vomiting • Specific varieties of meningitis – features readily visible on examination Acute bacterial meningitis • Onset is typically sudden, with rigors and a high fever • petechial rash, is strong evidence of meningococcal meninigitis • septicemia may present with acute septicemic shock • haemophilus influenzae type b infection has been virtually eliminated in developed countries by immunization Viral meningitis • Almost always a benign, self limiting condition lasting 4-10 days • headache may follow for some weeks there are no serious sequelae Chronic meningitis • Tuberculosis or cryptococcal meningitis commences with vague headache, anorexia and vomiting • meninigitic signs may take some weeks to develop • drowsiness, focal signs and seizures are common • syphilis, sarcoidosis and Behcet’s syndrome can also cause chronic meningits. In some cases a cause is never found Malignant meningitis • Malignant cells can cause a subacute or chronic non-infective meninigitic process • cranial nerve palsies, paraparesis and root lesions are seen, often in complex and fluctuating patterns • CSF cell count is raised, with high protein and low glucoses. • Treatment is with intrathecal cytotoxic agents, but the prognosis is poor Differential Diagnosis • Subarachnoid hemorrhage • Migraine • Acute meningitis • Intracranial mass lesion • Cerebral malaria Management • Ther recognition and immediate treatment of acute bacterial meningitis is vital • Condition is lethal, and even with optimal care the mortality is around 15% • Immediate parenteral antibiotic treatment should be given before any investigation • Combination of 3rd generation cephalosporin along with vancomycin for community acquired Meningitis • lumbar puncture is usually contraindicated if the clinical diagnosis is meningococcal disease Management • If there is any suspicion of an intracranial mass lesion, an immediate CT scan should be carried out • Immediate lumbar puncture should follow, if this is deemed safe • Blood should be taken for cultures and glucose level as well as for routine tests Management • Distinguish between viral, pyogenic, tuberculous and other organisms from the clinical setting and immediate examination of the CSF • In bacterial meningitis in children, dexamethasone is also given as this reduces the frequency of complications, particularly deafness Management • Tuberculous meningitis is treated for at least nine months with antituberculous drugs; rifampicin, isoniazid and pyrazinamide • local infection (e.g. an infected paranasal sinus) should be treated, surgically if necessary • surgical repair of depressed skull fracture or meningeal tear may be required Prophylaxis • Meningococcal infection condition should be notified to local public health authorities • prophylaxis of contacts with rifampicin • a vaccine is available against serogroup A and C meningococci Encephalitis • Encephalitis is inflammation of brain parenchyma • word usually implies viral infection by a wide variety of viruses Acute viral encephalitis • In many cases a viral etiology is persumed but not confirmed serologically or by culture • Usual organisms cultured from cases of viral encephalitis in adults are herpes simplex, Echo, Coxackie, mumps, Epstein-Barr viruses • Rabies is also variety of viral encephalitis Acute viral encephalitis • Japanese encephalitis in SE Asia • Rose River fever in Australia • California encephalitis in the USA • Omsk hemorrhagic fever in Russia • Tick-borne flavivirus encephalitis in Sweden and Central Europe Clinical Features • Many of these infections cause a mild self-limiting illness • fever • headache • mood change • drowsiness develop over several hours to several days • focal signs • seizures • coma • Death Differential Diagnosis • Bacterial meningitis with cerebral oedema and/or cerebral venous thrombosis • cerebral abscess • acute diseminated encephalomyelitis • cerebral malaria • toxic confusional states in febrile illnesses and in septicaemia Investigations • CT and MR imaging show diffuse areas of edema, often in the temporal lobes • ECG shows characteristic slow-wave changes • The CSF shows cells typical of a viral etiology • specific viral blood and CSF serology is helpful Treatment • Suspected herpes simplex encephalitis is immediately treated with intravenous acyclovir • supportive measures are required for comatose patients • seizures are treated with anticonvulsants • prophylactic immunization is possible against Japanese encephalitis and sometimes advised for travellers to endemic areas in South East Asia