Eduardo Baravalle 

The presence in the subarachnoid space of foreign elements, whether infectious, toxic, blood cells, or neoplastic, produces a meningeal syndrome. In this subarachnoid space circulate blood vessels in contact with cerebrospinal fluid (CSF), which also bathes the entire brain and spinal cord; as can be understood, a causative agent can spread to any site in the subarachnoid space. That is why meningeal syndromes are always cerebrospinal. When obstruction in the CSF circulation occurs, symptoms of intracranial hypertension may appear. On other occasions, the process may extend to the brain parenchyma and then symptoms and signs of encephalic involvement appear. Whatever the nature of the meningeal syndrome, the symptoms and signs will be similar.

Pathophysiology

The existence of foreign elements in the subarachnoid space produces hyperemia of the blood vessels, with increased permeability and the migration of neutrophils in the case of bacterial meningitis to the subarachnoid space. This exudate is increasing, particularly at the base of the brain and sheaths of the cranial and spinal sinuses. In the first days, polymorphonuclear cells can contain phagocytosed bacteria and later lymphocytes and histiocytes appear. Likewise, an increase in fibrinogen is observed, which is transformed into fibrin by the release of blood proteins from neutrophils and other cells of the inflammatory process. At this time, plasma cells appear and the exudate is arranged in two layers: an external one, together with the arachnoid, composed of polymorphonuclear cells and fibrin, and an internal one. together with the pia mater, composed of lymphocytes, plasma cells and macrophages. The fibroblasts organize the exudate with fibrin from the arachnoid. In the resolution phase of inflammation, cells disappear in the same order in which they appeared. Exudate from this process can block CSF circulation and cause hydrocephalus. In early studies, histology shows little change in the brain; after a few days an increase in astrocytes and microglia can be observed. In early studies, histology shows little change in the brain; after a few days an increase in astrocytes and microglia can be observed. In early studies, histology shows little change in the brain; after a few days an increase in astrocytes and microglia can be observed.

Classification

Meningitis can be classified as acute, subacute, and chronic. They will be subacute when the meningeal irritation proven by CSF alterations is greater than two weeks, and they will be chronic when it exceeds four weeks. According to the appearance of the CSF, they can be classified into meningitis with clear fluid and meningitis with purulent fluid.

Frequency

It affects both children and adults, and is more frequent in men than in women in a 3 to 1 ratio. In the US there are 40,000 cases annually with 10% mortality and 30% morbidity.

Symptoms and signs

Headache . It is usually occipital, moderate to severe with increasing and gravitational intensity. Sometimes it is pulsatile.

Vomiting . They are of cerebral origin, unexpected and easy, without prodrome, projectile. They are produced by hyperexcitability of the vomiting center.

Fever . It can be elevated and is sometimes not accompanied by tachycardia.

Photophobia . Patients reject light and pain may appear with eye movements.

Cutaneous hyperesthesia . When passing the finger over the patient's skin, a line is marked, called the meningeal line, which is produced by a vasomotor phenomenon.

Alterations of the state of consciousness . The patient may be lucid or have decreased consciousness, ranging from drowsiness to coma.

These alterations indicate brain involvement.

In children there may be hypothermia or fever. Mothers find them irritable, sleepy. And they can have seizures. swelling of the fontanelles, anorexia, vomiting, difficulty feeding and breathing.

In the elderly there may also be changes in character, less manifest alterations in body temperature and depressive symptoms.

Physical examination of patients with meningeal syndrome demonstrates muscle stiffness in the muscles of the neck, back, and lower limbs. That is why patients adopt the rifle trigger position; They are in lateral decubitus with the neck extended and the upper and lower limbs flexed. Sometimes there are opisthotonos.

The existing muscle contracture explains the presence of:

a) Kernig's sign : with the patient lying down, when trying to sit him up, flex the knees. Or while the patient is lying down, when flexing the hip the patient flexes the knees.

b) Brudzinski's sign : when trying to flex the neck, the patient in supine position flexes the hip and knee; The pupil may also dilate (Flalcau's sign). If flexion of the hip and knee is impeded. Extension of the thumb may occur with flexion of the rest of the fingers (Babinski's sign). When attempting to flex one knee and hip, the patient will make a similar movement on the other limb.

An ophthalmoscopic examination should be performed to check or rule out papilledema. Also, a rhinopharynx exam will be done looking for inflammatory signs or tumor masses.

In the questioning of these patients, the antibiotics received in the past will be evaluated, the existence of obvious infections, cough. hemoptysis, diarrhea, if you have undergone lumbar punctures, catheterizations or catheterizations. You will also be asked about the presence of arthritis, skin and mucosal lesions, and if you have a history of kidney disease, iridocyclitis, thrombophlebitis. breast nodules, abdominal pain, lymphadenopathy. splenomegaly and hemorrhagic symptoms.

Likewise, the concomitance of different viral diseases (ECHO, mumps, infectious mononucleosis, hepatitis) will be ruled out.

Study methodology

In addition to routine examinations, in which leukocytosis with neutrophilia or normal leukocytes with lymphomonocytosis and elevated erythrocytosis can be observed, the CSF must be studied using a lumbar puncture (Table 1).

Subacute and chronic meningeal syndromes

These syndromes are due to the prolongation of the life of patients with malignant or chronic diseases, the use of chemotherapy and antibiotics and the existence of patients with compromised immune systems. They have an insidious onset and neuroological pictures attributed to trivial processes. Mental disorders such as apathy, passivity. Drowsiness and confusion are sometimes confused with depression, old age, drug effects, fever, and metabolic disturbances. They are usually produced by opportunistic germs.

Complications

The picture can be complicated by intracranial hypertension due to ependymitis of the aqueduct of Silvio or the IV ventricle. Or with vasculitis that cause single or multiple infarcts, which will be manifested by motor or sensory or campimetric deficits, isolated or in combinations and of variable severity according to the location of the infarction. Injuries to the cranial nerves are more common in basal meningitis and frequently affect the common ocular motor. pathetic. external ocular and facial motor. Seizures are generally focal and occur as a consequence of heart attacks, abscesses, metastases, and parasitic cysts. Metabolic disturbances include dehydration and water intoxication; the most common is syndrome of inappropriate antidiuretic hormone secretion (seizures,