Acute Inflammation Of The Meninges
It is a medical condition characterized by acute inflammation of the meninges, a collective name of the three protective membranes that cover the spinal cord and the brain (). The most common causes of meningitis are the bacterial and viral infections; however, the condition may also be caused by drug allergies, fungi, chemical irritation, and cancer (). The most common clinical manifestations of meningitis are neck stiffness (44 -46 percent of the cases), severe headache (occurs in 90 percent of bacterial meningitis cases), and sudden high fever (44 -46 percent of the cases) (). These symptoms may also be accompanied by inability to tolerate loud noises (phonophobia) or light (photophobia), vomiting, coma, delirium, lethargy, sleepiness, nausea as well as altered consciousness (mental status) or confusion ().
However, in young children, only non-specific symptoms such as poor feeding, drowsiness, irritability, abnormal skin color, cold extremities, or leg pain may be exhibited (). In infants, hypotonia, high-pitched cry, paradoxic irritability, and bulging fontanelle may be observed (). Skin rash may also indicate a particular type of meningitis for instance one caused by the meningococcal bacteria (). The condition may trigger rapid breathing, high or abnormally low temperature, fast heart rate, systemic inflammatory syndrome due to falling blood pressure, sepsis, or adrenal glands hemorrhaging (). Other observable complications due to the condition include abnormal posturing, loss of the pupillary light reflex, and decreasing level of consciousness due to swelling, and herniation of the brain tissue (). Also hydrocephalus, weakness, hearing and visual loss, abnormal movement, loss of sensation, and seizures complications may be observed ()
Differential Diagnosis
Herpes Simplex Encephalitis (HSE)
HSE is a rare acute or sub-acute neurological disorder characterized by the brain (encephalitis) inflammation and causes both focal and general signs of cerebral dysfunction (). According to (), the HSE infection is thought to occur through the herpes simplex virus (HSV) direct neuronal transmission to the brain, from a peripheral site via the olfactory or trigeminal nerve (). However, the factors that precipice HSE and the exact pathogenesis of the condition are unknown ().
Subjective and Objective Findings
The clinical presentation of the HSE are largely similar to those of meningitis. It is important to note that there are no pathognomonic clinical findings that clearly distinguish the HSE disorder from other neurologic conditions that present similar symptoms and signs (). The most common clinical manifestations of the HSE disorder are memory loss (24 percent of the patients with the condition), focal weakness (33 percent), vomiting (46 percent), seizures (67 percent), psychiatric symptoms (71 percent), headache (81 percent), and fever (90 percent); these symptoms are similar to those observable in patients suffering from meningitis condition (). Other common clinical manifestations include papilledema (14 percent), visual field loss (14 percent), cranial nerve defects (32 percent), hemiparesis (38 percent), seizures (38 percent), ataxia (40 percent), dysphasia (76 percent), fever (92 percent), and alteration of consciousness (97 percent) ().
Just like in meningitis, HSE patients have a prodrome of nausea, seizures, and malaise accompanied by sub-acute or acute onset of encephalopathy whose symptoms include delirium, confusion, lethargy, and stupor (drowsiness with general weakness (). After the appearance of the initial symptoms mentioned above, the infected person may develop memory loss, anosmia (absence of the sense of smell), and diminished ability to communicate by signs (aphasia), writing, and/or speech (). Behavioral changes like psychotic episodes or hyperactivity may occur in some cases. Similar to meningitis, individual suffering from HSE may experience paralysis, convulsions, confusion, altered reflexes, and stiff neck (). Other severe symptoms common amongst HSE patients include retinitis (due to inflammation of the retina), hemiparesis (partial paralysis), hallucinations, and loss of consciousness (). However, the condition does not exhibit any skin lesions as is the case in some types of meningitis ().
Laboratory Test
In the diagnosis of HSE, the routine laboratory tests are usually not helpful. They are only used to detect renal disease or show evidence of infection. HSE diagnosis can only be confirmed through brain biopsy or Polymerase chain reaction (PCR). Some of the laboratory tests that may be helpful in the diagnosis of HSE are:
1) Quantification of intrathecal antibodies
2) Vesicular lesions’ Tzanck preparations
3) Serologic analysis of blood or CSF
Images Test
HSE is evaluated through three major imaging tests which are:
1) Electroencephalography (EEG) (has 84 percent sensitivity and 32 percent specificity to HSE abnormal patterns).
2) computerized tomography (CT) scan of the brain (the procedure is less sensitive compared to MRI)
3) Magnetic resonance imaging (MRI). It is the most preferred image test for HSE