What is Autoimmune Encephalitis
Automimmune Encephalitis is a serious medical condition in which the immune system attacks the brain, impairing function. With rapid diagnosis and appropriate treatment, many patients recover most or all functions. However, not all patients experience full recovery; few patients never regain significant brain and/or bodily functions.
The disease occurs in men, women and children of all ages, but it has historically been diagnosed most frequently in young women. An older study suggests that out of 100-plus known autoimmune diseases, 75% of people affected are female.
The direct cause of most cases of AE remains unknown. However the following have been shown to trigger AE:
- a teratoma ( a type of tumor, generally found in the ovaries);
- the presence in the body of a cancer, that indirectly triggers an autoimmune response (this is called a “paraneoplastic syndrome”)
- exposure to certain common bacteria, including, but not limited to, streptococcus and mycoplasma pneumonia, with or without active infection.
Antibody associated CNS Diseases: New Developments
The finding of Neurologic Specific auto-antibodies is a cornerstone in a new classification of the disease. It also enables a more rational therapeutic strategy.
- Intrathecal synthesis of specific auto-antibodies can be a feature of some autoimmune encephalitis.
- These disorders may be with or without association to a neoplasm.
- Paraneoplastic auto-antibodies are always markers of neoplasia under development, although not necessarily markers of a neurological disorder.
- Rapid diagnostic procedures and commencement of therapy can be of major significance.
World over, different types of autoimmune encephalitis have been identified in the laboratory. Metropolis Healthcare Ltd provides diagnostic tests for Autoimmune Encephalitis and assures fast TAT, correlation with neurologist and immunologist.
Neurodegenerative disease is an umbrella term for a range of conditions which primarily affect the neurons in the human brain.
Neurons are the building blocks of the nervous system which includes the brain and spinal cord. Neurons normally don’t reproduce or replace themselves, so when they become damaged or die they cannot be replaced by the body. Examples of neurodegenerative diseases include Parkinson’s, Alzheimer’s, and Huntington’s disease.
Neurodegenerative diseases are incurable and debilitating conditions that result in progressive degeneration and / or death of nerve cells. This causes problems with movement (called ataxias), or mental functioning (called dementias).
In this section, we would be looking at Huntington’s and Wilsons Disease in detail
Huntington’s disease is an inherited disease that causes the progressive breakdown (degeneration) of nerve cells in the brain. Huntington’s disease has a broad impact on a person’s functional abilities and usually results in movement, thinking (cognitive) and psychiatric disorders. Huntington’s disease is caused by an inherited defect in a single gene. Huntington’s disease is an autosomal dominant disorder, which means that a person needs only one copy of the defective gene to develop the disorder.
Movement disorders include Involuntary jerking or writhing movements, Muscle problems, such as rigidity, Slow or abnormal eye movements, Impaired gait, posture and balance, Difficulty with the physical production of speech or swallowing.
Impairments in voluntary movements — rather than the involuntary movements — may have a greater impact on a person’s ability to work, perform daily activities, communicate and remain independent.
Cognitive impairments include Difficulty organizing, prioritizing or focusing on tasks, Lack of flexibility or the tendency to get stuck on a thought, behavior or action, Lack of impulse control that can result in outbursts, acting without thinking, Lack of awareness of one’s own behaviors and abilities, Slowness in processing thoughts or ”finding” words and Difficulty in learning new information.
Psychiatric disorders include Feelings of irritability, sadness or apathy, Social withdrawal, Insomnia, Fatigue and loss of energy, Frequent thoughts of death, dying or suicide
Genetic counseling and testing
If symptoms strongly suggest a diagnosis of Huntington’s disease, your doctor may recommend a genetic test for the defective gene. This test can confirm the diagnosis, and it may be valuable if there’s no known family history of Huntington’s disease or if no other family member’s diagnosis was confirmed with a genetic test. Before undergoing such a test, the genetic counselor will explain the benefits and drawbacks of learning test results. The genetic counselor can also answer questions about the inheritance patterns of Huntington’s disease.
Predictive genetic test: A genetic test can be given to someone who has a family history of the disease but shows no signs or symptoms. This is called predictive testing. The test result has no treatment benefit, and it doesn’t indicate when disease onset will begin or what symptoms are likely to appear first. Some people may elect to do the test because they find it more stressful not knowing. Others may want to take the test before they make decisions about having children. These tests are only performed after consultation with a genetic counselor.
Wilson’s disease is a rare inherited disorder that causes too much copper to accumulate in your liver, brain and other vital organs. Symptoms typically begin between the ages of 12 and 23. Copper plays a key role in the development of healthy nerves, bones, collagen and the skin pigment melanin. Normally, copper is absorbed from your food, and any excess is excreted through bile — a substance produced in your liver.
But in people with Wilson’s disease, copper isn’t eliminated properly and instead accumulates, possibly to a life-threatening level. When diagnosed early, Wilson’s disease is treatable, and many people with the disorder live normal lives.
Ataxia: Spinocerebellar, Neurogenic, Friedreich, Autosomal
Spinocerebellar ataxia (SCA), also known as spinocerebellar atrophy or spinocerebellar degeneration, is a progressive, degenerative, genetic disease with multiple types, each of which could be considered a disease in its own right. SCA is hereditary, progressive, degenerative, and often fatal. There is no known effective treatment or cure. SCA can affect anyone of any age. The disease is caused by either a recessive or dominant gene. In many cases people are not aware that they carry a relevant gene until they have children who begin to show signs of having the disorder.
Spinocerebellar ataxia (SCA) is one of a group of genetic disorders characterized by slowly progressive incoordination of gait and is often associated with poor coordination of hands, speech, and eye movements. A review of different clinical features among SCA subtypes was recently published describing the frequency of non-cerebellar features, like parkinsonism, chorea, pyramidalism, cognitive impairment, peripheral neuropathy, seizures, among others. As with other forms of ataxia, SCA frequently results in atrophy of the cerebellum, loss of fine coordination of muscle movements leading to unsteady and clumsy motion, and other symptoms.
The symptoms of an ataxia vary with the specific type and with the individual patient. In general, a person with ataxia retains full mental capacity but progressively loses physical control.
Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome is a clinically heterogeneous progressive condition characterized by a combination of proximal neurogenic muscle weakness, sensory-motor neuropathy, ataxia, and pigmentary retinopathy.
Diagnosis is based on clinical manifestations, electroretinogram, and genetic testing. Peripheral neuropathy may be demonstrated by electromyography, whereas an MRI may pick up cerebral and cerebellar atrophy in later stages. Serum lactate may be normal or elevated.
As NARP syndrome is progressive, patients may become increasingly dependent of others. The quality of life is severely reduced. Patients may go blind and deaf and may experience depression and dementia. Due to the progressive neurogenic muscle weakness patients may become wheelchair bound.
Friedreich’s ataxia is an autosomal recessive inherited disease that causes progressive damage to the nervous system. It manifests in initial symptoms of poor coordination such as gait disturbance; it can also lead to scoliosis, heart disease and diabetes, but does not affect cognitive function. The disease is progressive, and ultimately a wheelchair is required for mobility.
The ataxia of Friedreich’s ataxia results from the degeneration of nervous tissue in the spinal cord, in particular sensory neurons essential (through connections with the cerebellum) for directing muscle movement of the arms and legs. The spinal cord becomes thinner and nerve cells lose some of their myelin sheath (the insulating covering on some nerve cells that helps conduct nerve impulses).
Symptoms typically begin sometime between the ages of 5 to 15 years, but in Late Onset FA may occur in the 20s or 30s. Symptoms include any combination, but not necessarily all, of the following:
- Muscle weakness in the arms and legs
- Loss of coordination
- Vision impairment
- Hearing impairment
- Slurred speech
- Curvature of the spine (scoliosis)
- High plantar arches (pes cavus deformity of the foot)
- Diabetes (about 20% of people with Friedreich’s ataxia develop carbohydrate intolerance and 10% develop diabetes mellitus)
Autosomal dominant cerebellar ataxia (ADCA) is a form of spinocerebellar ataxia inherited in an autosomal dominant manner. ADCA is a genetically inherited condition that causes deterioration of the nervous system leading to disorder and a decrease or loss of function to regions of the body.
Degeneration occurs at the cellular level and in certain subtypes results in cellular death. Cellular death or dysfunction causes a break or faulty signal in the line of communication from the central nervous system to target muscles in the body. When there is impaired communication or a lack of communication entirely, the muscles in the body do not function correctly. Muscle control complications can be observed in multiple balance, speech, and motor or movement impairment symptoms. ADCA is divided into three types and further subdivided into subtypes known as SCAs (spinocerebellar ataxias)
A demyelinating disease is any condition that results in damage to the protective covering (myelin sheath) that surrounds nerve fibres in your brain and spinal cord. When the myelin sheath is damaged, nerve impulses slow or even stop, causing neurological problems.
Multiple sclerosis: Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system. In this disorder, your immune system attacks the myelin sheath or the cells that produce and maintain it. This causes inflammation and injury to the sheath and ultimately to the nerve fibers that it surrounds and may result in multiple areas of scarring (sclerosis).
Neuromyelitis optica (Devic’s disease) — inflammation and demyelination of the central nervous system, especially of the optic nerve and spinal cord. Neuromyelitis optica (NMO), also known as Devic’s disease or Devic’s syndrome, is a heterogeneous condition consisting of the simultaneous inflammation and demyelination of the optic nerve (optic neuritis) and the spinal cord (myelitis). It can be monophasic or recurrent. The main symptoms of Devic’s disease are loss of vision and spinal cord function. Optic neuritis may manifest as visual impairment with decreased visual acuity, although visual field defects, or loss of color vision may occur in isolation or prior to formal loss of acuity. Spinal cord dysfunction can lead to muscle weakness, reduced sensation, or loss of bladder and bowel control.
MS and other demyelinating diseases most commonly result in vision loss, muscle weakness, muscle stiffness and spasms, loss of coordination, loss of sensation, pain, and changes in bladder and bowel function..
Peripheral Neuropathies – Guillain Barre Syndrome
Peripheral neuropathy, a result of damage to your peripheral nerves, often causes weakness, numbness and pain, usually in your hands and feet. It can also affect other areas of your body. Your peripheral nervous system sends information from your brain and spinal cord (central nervous system) to the rest of your body. Peripheral neuropathy can result from traumatic injuries, infections, metabolic problems, inherited causes and exposure to toxins. One of the most common causes is diabetes mellitus.
People with peripheral neuropathy generally describe the pain as stabbing, burning or tingling. In many cases, symptoms improve, especially if caused by a treatable condition. Medications can reduce the pain of peripheral neuropathy.
Guillain-Barré (ghee-yan bah-ray) syndrome (GBS) is a rare inflammatory disorder in which the body’s immune system attacks the protective covering of the peripheral nerves (myelin sheath), preventing the nerves from sending signals to the muscles. It can develop over the course of several hours or days, or it may take up to 3 or 4 weeks. It is the most common cause of rapidly acquired paralysis and should be treated as a condition requiring urgent diagnosis and treatment.
The first symptoms of GBS usually include varying degrees of weakness or tingling sensations in the legs. In many instances, the weakness and abnormal sensations ascend and spread to the arms and upper body. Although many cases are mild, these symptoms can increase in intensity until the muscles cannot be used at all and the patient is almost totally paralyzed. In extreme cases, the patient has difficulty breathing and must be placed on a ventilator. If the throat and face are affected, a feeding tube may be required. In some cases, peripheral neuropathy may develop.
GBS improves spontaneously, but the recovery period may take from several weeks to more than a year. Most patients make a total recovery, from even the most severe cases of GBS, although some continue to have a certain degree of weakness, numbness or occasional pain.
Duchennne Muscular Dystrophy
Muscular dystrophies are a group of diseases that make muscles weaker and less flexible over time. Duchenne muscular dystrophy (DMD) is the most common type. It’s caused by flaws in the gene that controls how the body keeps muscles healthy.
The disease almost always affects boys, and symptoms usually begin early in childhood. Children with DMD have a hard time standing up, walking, and climbing stairs. Many eventually need wheelchairs to get around. They can also have heart and lung problems.
If your child has DMD, you’ll probably notice the first signs before he turns 6 years old. Muscles in the legs are usually some of the first affected, so he’ll probably start to walk much later than other children his age. Once he can walk, he may fall down often and have trouble climbing stairs or getting up from the floor. After a few years, he might also begin to waddle or walk on his toes.
If the doctor suspects DMD, he’ll do some other tests, including:
Blood tests. The doctor will take a sample of your child’s blood and test it for creatine kinase, an enzyme that your muscles release when they are damaged. A high CK level is a sign that your child could have DMD.
Gene tests. Doctors can also test the blood sample to look for a change in the dystrophin gene that causes DMD. Girls in the family can get the test to see if they carry this gene..
Neuromuscular Junction Disorders (Myasthenia Gravis, Lambert – Eaton)
Neuromuscular junction disease is a medical condition where the normal conduction through the neuromuscular junction fails to function correctly.
Myasthenia Gravis Muscle weakness caused by myasthenia gravis worsens as the affected muscle is used repeatedly. Because symptoms usually improve with rest, your muscle weakness may come and go. However, myasthenia gravis symptoms tend to progress over time, usually reaching their worst within a few years after the onset of the disease.
Eye muscles: In more than half the people who develop myasthenia gravis, their first signs and symptoms involve eye problems, such as: Drooping of one or both eyelids (ptosis), Double vision (diplopia), which may be horizontal or vertical, and improves or resolves when one eye is closed.
Face and throat muscles: In about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can cause:
Altered speaking. Your speech may sound very soft or nasal, depending upon which muscles have been affected.
Difficulty swallowing. You may choke very easily, which makes it difficult to eat, drink or take pills. In some cases, liquids you’re trying to swallow may come out your nose.
Problems chewing. The muscles used for chewing may wear out halfway through a meal, particularly if you’ve been eating something hard to chew, such as steak.
Limited facial expressions. Your family members may comment that you’ve “lost your smile” if the muscles that control your facial expressions have been affected.
Neck and limb muscles: Myasthenia gravis can cause weakness in your neck, arms and legs, but this usually happens along with muscle weakness in other parts of your body, such as your eyes, face or throat.
The disorder usually affects arms more often than legs. However, if it affects your legs, you may waddle when you walk. If your neck is weak, it may be hard to hold up your head.
Blood analysis: A blood test may reveal the presence of abnormal antibodies that disrupt the receptor sites where nerve impulses signal your muscles to move.
Lambert Eaton Syndrome: Lambert-Eaton syndrome (LES) is a rare disorder in which faulty communication between nerves and muscles leads to muscle weakness. LES is an autoimmune disorder. This means your immune system mistakenly targets healthy cells and tissues in the body. With LES, antibodies produced by the immune system attack nerve cells. This makes nerves cells unable to release enough of a chemical called acetylcholine. This chemical transmits impulses between nerves and muscles. The result is muscle weakness.
Symptoms: Weakness or loss of movement that can be more or less severe, including: Difficulty climbing stairs or lifting things, Drooping of the head, The need to use the hands to get up from a sitting or lying position, Problems talking, Problems chewing or swallowing, which may include gagging or choking, Vision changes, such as blurry vision, double vision, and problem keeping a steady gaze, Blood pressure changes, Dizziness upon standing, Dry mouth
LES may occur with cancers such as small cell lung cancer or autoimmune disorders such as vitiligo, which leads to a loss of skin pigment.
Cerebral Venus Thrombosis
Cerebral venous sinus thrombosis (CVST) is the presence of acute thrombosis (a blood clot) in the dural venous sinuses, which drain blood from the brain. Symptoms may include headache, abnormal vision, any of the symptoms of stroke such as weakness of the face and limbs on one side of the body, and seizures. The diagnosis is usually by computed tomography (CT/CAT scan) or magnetic resonance imaging (MRI) employing radiocontrast to demonstrate obstruction of the venous sinuses by thrombus.
Cerebral venous sinus thrombosis is more common in particular situations.
Thrombophilia, a tendency to develop blood clots due to abnormalities in coagulation, e.g. factor V Leiden, deficiency of protein C, protein S or antithrombin, or related problems
Deep Vein Thrombosis: Deep vein thrombosis (DVT) occurs when a blood clot (thrombus) forms in one or more of the deep veins in your body, usually in your legs. Deep vein thrombosis can cause leg pain or swelling, but may occur without any symptoms.
Deep vein thrombosis can develop if you have certain medical conditions that affect how your blood clots. Deep vein thrombosis can also happen if you don’t move for a long time, such as after surgery, following an accident, or when you are confined to a hospital or nursing home bed.
Deep vein thrombosis is a serious condition because blood clots in your veins can break loose, travel through your bloodstream and lodge in your lungs, blocking blood flow (pulmonary embolism)..
CNS Vasculitis Associated Antibodies
Vasculitis is the inflammation (swelling) of the blood vessels, the network of hollow tubes that carry blood throughout the body. Central nervous system (CNS) vasculitis is inflammation of blood vessel walls in the brain or spine. (The brain and the spine make up the central nervous system.) CNS vasculitis often occurs in the following situations:
- Accompanied by other autoimmune diseases such as systemic lupus erythematosus, dermatomyositis, and, rarely, rheumatoid arthritis;
- Infection, such as viral or bacterial;
- Systemic (affecting the whole body) vasculitic disorders (Wegener’s granulomatosis, microscopic polyangiitis, Behçet’s syndrome);
- It can occur without any associated systemic disorder. In this case, the vasculitis is only confined to the brain or the spinal cord and it is referred to as primary angiitis of the CNS (PACNS).
Spinal Muscular Atrophy
Spinal muscular atrophy (SMA) is a genetic disease that attacks nerve cells, called motor neurons, in the spinal cord. These cells communicate with your voluntary muscles – the ones you can control, like in your arms and legs. As the neurons die, the muscles weaken. This can affect walking, crawling, breathing, swallowing, and head and neck control. SMA runs in families. Parents usually have no symptoms, but still carry the gene. Genetic counseling is important if the disease runs in your family. There are many types of SMA. Some of them are fatal. Some people have a normal life expectancy. It depends on the type and how it affects breathing. There is no cure. Treatments help with symptoms and prevent complications. They may include machines to help with breathing, nutritional support, physical therapy, and medicines.
In a broad sense, these syndromes are collections of symptoms that result from substances produced by the tumor, and they occur remotely from the tumor itself. The symptoms may be endocrine,  neuromuscular or musculoskeletal, cardiovascular, cutaneous, hematologic, gastrointestinal, renal, or miscellaneous in nature. Paraneoplastic syndromes may be the first or most prominent manifestation of a cancer. When a patient without a known cancer presents with one of the “typical” paraneoplastic syndromes, a diagnosis of cancer should be considered and investigated. Because of their protean manifestations, paraneoplastic syndromes should be managed by a coordinated team of physicians, including medical oncologists, surgeons, radiation oncologists, endocrinologists, hematologists, neurologists, and dermatologists.
Signs and symptoms of paraneoplastic syndromes of the nervous system can develop relatively quickly, often over days to weeks and may include: Difficulty walking, Difficulty maintaining balance, Loss of muscle coordination, Loss of muscle tone or weakness, Loss of fine motor skills, such as picking up objects, Difficulty swallowing, Slurred speech or stuttering, Memory loss and other thinking (cognitive) impairment, Vision problems, Sleep disturbances, Seizures, Hallucinations, Unusual involuntary movements. .
Early treatment of bacterial meningitis can prevent serious complications.
Early meningitis symptoms may mimic the flu (influenza). Symptoms may develop over several hours or over a few days.
Possible signs and symptoms in anyone older than the age of 2 include:
Sudden high fever, Stiff neck, Severe headache that seems different than normal, Headache with nausea or vomiting, Confusion or difficulty concentrating, Seizures, Sleepiness or difficulty waking. Sensitivity to light, No appetite or thirst, Skin rash (sometimes, such as in meningococcal meningitis).
Viral infections are the most common cause of meningitis, followed by bacterial infections and, rarely, fungal infections. Because bacterial infections can be life-threatening, identifying the cause is essential.
Bacteria that enter the bloodstream and travel to the brain and spinal cord cause acute bacterial meningitis. But it can also occur when bacteria directly invade the meninges. This may be caused by an ear or sinus infection, a skull fracture, or, rarely, after some surgeries.
Several strains of bacteria can cause acute bacterial meningitis, most commonly:
Streptococcus pneumoniae (pneumococcus), Neisseria meningitidis (meningococcus), Haemophilus influenzae (haemophilus), Listeria monocytogenes (listeria).
Viral meningitis is usually mild and often clears on its own. Most are caused by a group of viruses known as enteroviruses, which are most common in late summer and early fall. Viruses such as herpes simplex virus, HIV, mumps, West Nile virus and others also can cause viral meningitis.
Slow-growing organisms (such as fungi and Mycobacterium tuberculosis) that invade the membranes and fluid surrounding your brain cause chronic meningitis. Chronic meningitis develops over two weeks or more. The symptoms of chronic meningitis — headaches, fever, vomiting and mental cloudiness — are similar to those of acute meningitis.
Fungal meningitis is relatively uncommon and causes chronic meningitis. It may mimic acute bacterial meningitis. Fungal meningitis isn’t contagious from person to person. Cryptococcal meningitis is a common fungal form of the disease that affects people with immune deficiencies, such as AIDS. It’s life-threatening if not treated with an antifungal medication.
Herpes simplex encephalitis (HSE) is an acute or subacute illness that causes both general and focal signs of cerebral dysfunction. Brain infection is thought to occur by means of direct neuronal transmission of the virus from a peripheral site to the brain via the trigeminal or olfactory nerve. The exact pathogenesis is unclear, and factors that precipitate HSE are unknown.
Signs and symptoms
Patients with HSE may have a prodrome of malaise, fever, headache, and nausea, followed by acute or subacute onset of an encephalopathy whose symptoms include lethargy, confusion, and delirium. However, no pathognomonic clinical findings reliably distinguish HSE from other neurologic disorders with similar presentations.
The following are typically the most common symptoms of HSE
Fever, Headache, Psychiatric symptoms, Seizures, Vomiting, Focal weakness ,Memory loss
Real time PCR tests along with MRI, CT and biopsies are useful in diagnosis.
Infectious manifestations referring to the CNS are multiple and include myelopathy, encephalitis, meningitis, and vasculopathy. The possibility of infectious reactivation without the characteristic vesicular rash (zoster sine herpete) makes the diagnosis even more difficult.
CMV spreads very easily. Infected people may shed the virus in their urine or saliva for months. The virus is also excreted in cervical mucus, semen, stool, and breast milk. Thus, the virus is spread through sexual and nonsexual contact. If a pregnant woman is infected, the fetus may acquire the infection during the pregnancy, or the baby may acquire the infection during delivery. CMV infection may develop in people who receive a transfusion of infected blood or an infected organ transplant. Most people infected with CMV have no symptoms. A few infected people feel ill and have a fever. If a person receives a transfusion of blood containing CMV, fever and sometimes liver inflammation may develop 2 to 4 weeks later.
CMV infection may develop gradually and not be recognized immediately. Diagnosis is often unnecessary in healthy adults and children because treatment is unnecessary. However, doctors always consider the possibility of CMV infection in people who have fever and fatigue or who have a weakened immune system and an eye, a brain, or a gastrointestinal infection. CMV infection is also suspected in newborns who have a fever or who seem sick.
Once CMV infection is suspected, a doctor conducts tests to detect the virus in body fluids or tissues. In newborns, the diagnosis is usually made by culturing the urine.Blood tests that detect antibodies to CMV can confirm a new infection but cannot confirm disease caused by reactivation of the virus, as often occurs in people with a weakened immune system. In these people, a biopsy of affected tissues is often necessary to confirm CMV infection. Blood tests to estimate how many viruses are present may also be done.
Measles, Mumps and Rubella Infections
Mumps infection and Encephalitis
Mumps virus frequently infects the central nervous system. Before the MMR vaccine was introduced mumps used to be the most common cause of admission to hospital with meningitis or encephalitis, occurring in 1 in 200-5,000 children. Mumps also causes deafness. MMR vaccine has had a dramatic impact and hardly any children are admitted to hospital with mumps these days.
Rubella virus and Encephalitis
Rubella virus causes severe brain injury in children if their mother is infected in early pregnancy. The brain injury is caused by meningoencephalitis, part of the “congenital rubella syndrome”. Rubella virus can also cause a progressive “pan-encephalitis” later in life in children who were infected in the womb and survived but remain chronically infected. Few young mothers will have any personal experience of the effects of rubella today, which were well known in the past. Immunisation with a rubella containing vaccine, including MMR vaccine, offers high levels of protection against disease. Rubella is now very rare in the UK with only one or two pregnant women exposed to the virus each year. This is one of the great successes of MMR vaccine.
CNS infections – Viral
Infection of the nervous system can involve the meninges (meningitis) or the brain substance itself (encephalitis), or both (meningoencephalitis). Additionally, infections can be acute or chronic. The organisms that are involved in infection are bacterial, parasitic or viral.
Viral infections of the central nervous system (CNS) include both acute and chronic conditions caused by a broad range of different viruses. The most common infections globally include EBV (Epstein Barr Virus), Enteroviruses, Parovirus B19, JEV (Japanese Encephalitis Virus). Others include Herpes Simplex Virus, Cytomegalovirus, Human Herpesvirus.
Patients present with acute fever, headache and signs of meningeal irritation, e.g. photophobia and neck stiffness. The prognosis is usually excellent. Cerebrospinal fluid (CSF) polymerase chain reaction (PCR) testing can be performed for diagnosis. Treatment is largely supportive.
CSF polymerase chain reaction (PCR)
PCR testing has revolutionised the diagnosis of viral CNS infections. It can be performed for many viruses including herpes viruses (HSV, VZV, CMV, EBV), enterovirus, JC virus and mumps. False negative and false positive may occur and should be correlated clinically. .
CNS Parasitic Infections
Parasitic infections of the central nervous system (CNS) include two broad categories of infectious organisms: single-celled protozoa and multicellular metazoa. The parasites can be identified by conventional histology, immunohistochemistry, in situ hybridization, and PCR.
The most commonly observed parasitic infections include that of Cysticerus, Echinococcus and Toxoplasma.
Cysticercosis: Tanium solium exhibits a worldwide distribution. Invasion of the central nervous system (i.e., neurocysticercosis) is an important cause of human morbidity, and occasional mortality. Although this parasite is generally well tolerated while it is alive, its death triggers inflammation and edema. The clinical presentation of neruocysticercosis is varied and depends on the stage, number, size and locations of the cysticerci with the CNS and the immune response against the parasite. Epileptic seizures are the commonest manifestation of neurocysticercosis. Seizures occur in 50-80% of patient with brain cysts. Neurocysticercosis can also present with intracranial hypertension or hydrocephalus. These syndromes are related to a blockage of the circulation of cerebralspinal fluid (CSF). Occasionally a cyst will grow larger than the usual 1-2 cm and will mimic a tumor.
Serological tests can also be used to detect T. solium antibodies in the serum or CSF. However, there are problems with sensitivities and crossreactions with other parasitic worms. Accurate diagnosis depends on a combination of clinical, epidemiologic, radiographic and immunological information.
Cerebral Hyatid Disease – Echinococcus:
Cerebral hydatid disease (neurohydatidosis) is caused by Echinococcus granulosus or less commonly E. alveolaris or E. multilocularis. The larval stage is the cause of hydatid disease in humans. Cerebral hydatid disease is a rare parasitic infestation and accounts for 1-2 % of all cystic echinococcosis. The infection is acquired via contaminated food with eggs of the tapeworm.
Symptoms and signs include: focal neurological deficits, headaches, increased intracranial pressure, hydrocephalus, loss of vision, altered mental status, seizures (rare)
Serology and histopathology of the excised cyst will confirm the diagnosis of neurohydatidosis.
Toxoplasma gondii is a coccidian parasite which infects humans as well as a wide variety of mammals and birds. It exhibits a predator-prey type life cycle and felines are the only definitive host. Toxoplasmosis is found throughout the world, except for extremely cold or dry climates, but tends to be more prevalent in tropical climates like India.
Congenital (ie, transplacental) infections are more likely to be symptomatic and can be severe. Congenital transmission can only occur during an acute infection (ie, tachyzoites) acquired during pregnancy. Mothers with a chronic infection acquired before the pregnancy are not at a risk for transmitting Toxoplasma. One-third of mothers acquiring the infection during pregnancy will pass the infection to fetus. Severity of disease varies with age of fetus and is more severe early in pregnancy. However, transmission is more frequent later in pregnancy. Congenital infection can result in: spontaneous abortion, premature birth, or full-term birth with or without overt symptoms.
Typical disease manifestations include: retinochoroiditis, psychomotor disturbances, intracerebral calcification, hydrocephaly, and microcephaly. Ocular symptoms due to retinochoroiditis are particularly common. Twenty percent will exhibit symptoms at birth and 82% will develop symptoms by adolescence.
Diagnosis of toxoplasmosis is rarely made through the detection or recovery of organisms, but relies heavily on serological procedures. Parasites can bedetected in biopsied specimens or cerebral spinal fluid.