**2. Meningitis and its treatment**

Meningitis is the term used to describe the inflammation of the meninges anywhere in the neural axis. The inflammation can be caused by viral, bacterial or even fungal pathogens, sterile meningitis is a form of inflammation of the leptomeninges where the patient is clinically having symptoms of meningitis, but leukocytosis is not seen in CSF analysis and no pathologic pathogen can be cultured from the CSF. The most common route of infection is usually the spread of pathogens via the hematogenous pathway after upper respiratory tract infections as well as transmission of bacteria from adjacent ongoing infections via the emissary veins from the nearby structures to the meninges (e.g. sinusitis, mastoiditis, odontogenic infections, otitis media), intra or post-operative contamination of the intracranial structures (e.g. after neurosurgical interventions) is another common way of transmission for these pathogens, skull base fractures are also a source for bacterial inoculation and can cause meningitis. In the following section we will be discussing the most common bacterial and viral pathogens causing meningitis.

#### **2.1 Bacterial meningitis**

Bacterial meningitis is a serious CNS infection which can be life threatening if left untreated or not treated properly. Various pathogens can cause meningitis in various age groups, in this section for the sake of simplicity we will be describing the most common adult pathogens and their treatments in details.

The common pathogens causing meningitis are, *Streptococcus pneumoniae*, Neisseria meningitidis, group B Streptococcus spp., *Listeria monocytogenes*, and Haemophilus influenzae. *Streptococcus pneumoniae* is usually causing meningitis in adults and children, neonates and infants are generally not infected by this

*Infections in Neurosurgery and Their Management DOI: http://dx.doi.org/10.5772/intechopen.99115*

microorganism. Patients who suffer from skull base fractures and have CSF leaks often develop meningitis due to S. pneumonia inoculation [3]. This so-called community acquired bacterial meningitis (CABM) is considered as a rare pathology with high mortality and morbidity rates. The prevalence of this disorder has decreased significantly in the past decades due to administration of conjugate vaccines and more efficient diagnostic methods and treatments. The most comm pathogens causing CABM are *S. pneumoniae*, N. meningitidis, L monocytogenes according to a study published by Tubiana et al. in 2020 [4].

The diagnosis of CABM is based on clinical findings, CSF analysis and complete blood count (CBC) findings, MRI scans can be useful for obtaining more information about the extent and severity of meningitis but not necessary for establishing the diagnosis. **Figure 1** shows alterations on brain MRI scans in a patient with severe meningococcal meningitis.

Once the diagnosis is confirmed, empirical broad-spectrum antibiotics based on local bacterial resistance should be started and afterwards modified based on antibiograms. For initial treatment third generation cephalosporins [4] alongside amoxicillin or ampicillin to cover treatment for L monocytogenes are recommended and once antibiotic susceptibility results are available then targeted therapy should be started with agents having higher CSF penetration; Steroids and C5 antibodies are also recommended, in case the ongoing infection is not responding well to systemic antibody treatment [5].

#### **2.2 Post-operative**

Post-operative meningitis or post neurosurgical meningitis (PNM) is a complication of cranial surgery, and its rate of occurrence is depending on multiple factors. We will be discussing the most common factors contributing to the occurrence of postoperative meningitis and its treatment. Surgeries are done in aseptic environment, careful disinfection of the surgical site and keeping the aseptic environment while performing the surgery is the most important factor in preventing postoperative meningitis. Studies have shown that shaving hair within the surgical site has little to no effect in decreasing postoperative infections [6], but regardless of this fact it is highly recommended to have surgical site free of hair in order to

#### **Figure 1.**

*Diffuse contrast enhancement of the arachnoid membrane and dura bilaterally in the fronto-temporal region is seen in a patient with meningococcal meningitis. The Arachnoiditis is a complication and sequel of untreated or very severe aggressive meningitis.*

#### *Infections and Sepsis Development*

achieve better and easier access to the site. Prophylactic antibiotic administration is also an important key in preventing postoperative infections, however its use can be controversial as there are studies indicating that prophylactic antibiotic administration before surgery has little to no effect on preventing post-operative infections. The use of administration of antibiotics are usually depending on the existing local bacterial resistance patterns, individual skin flora, type and location of the surgery.

Usage of broad-spectrum antibiotics for cranial surgeries are not recommended simply because their use has not shown any advantage over other antibiotics; Cefazolin has been used for many years now for prophylactic purposes in cranial surgery. If multi resistant *Staphylococcus aureus* (MRSA) is present in the institute where the procedure is carried out or if the skin floral composition of the patient includes MRSA, then administration of Vancomycin is recommended supplementary to Cefazolin [7]. Since implanting foreign bodies both in cranial and spinal surgeries are quite often, it is important to handle the instruments and implants with care to maintain a fully aseptic environment.

One of the important factors contributing to prevention of the postoperative infections is wound closure and surgical wound management; An efficient watertight wound closure ensures proper anatomical closure of layers, minimizing the risk of infections in deeper layers and by proper management of the surgical wound the risk of superficial wound infection can be reduced drastically. It should be noted that patients scheduled for elective surgery should be screened for the presence of multi resistant bacteria in their flora. Patients with multi resistant bacterial composition should be isolated before and after surgery in order to decrease the transmission of the multi resistant bacteria to other patients and the medical staff. Disposable protective clothing should be used by medical staff in order to minimize the risk of transmission.

If signs and symptoms of surgical site wound infection are seen, a CBC and superficial and deep wound sampling for microbiological culturing are necessary. Empirical antibiotic treatment should be started and then modified based on the antibiogram results of culturing. After cranial surgery if signs and symptoms of meningitis are present, then LP should be performed for analysis. Slight elevations of WBC in CSF (up to 50 cells mm3) usually do not require prompt antibiotic treatment, symptomatic treatment for headache, nausea and vomiting and hydration are recommended, leukocytosis should be controlled and if a rise in WBCs count is seen then antibiotic treatment should be started. For values above 50 cells per mm3 empirical antibiotic should be considered and then modified based on culture results if needed. If severe leukocytosis in CSF is seen (above 1000 WBCs per mm3) or if systematic treatment is not achieving desired results, intrathecal antibiotic administration should be considered. Empirical treatment for PNM should include Vancomycin for the coverage of staphylococci and P. acnes, as well as a cephalosporin or carbapenem to cover gram negative bacteria and in particularly pseudomonas [8].

Postoperative meningitis after cranial surgeries can cause local osteomyelitis at the level of surgery and/or subdural empyema or cerebral abscess formation. These complications will be discussed in the upcoming sections.

#### **2.3 Viral**

Viral meningitis is not a common finding in neurosurgical wards, and its route of infection and treatment is usually different from PNM and bacterial routes, therefore this topic is not relevant to our discussion, and it will not be discussed here.

*Infections in Neurosurgery and Their Management DOI: http://dx.doi.org/10.5772/intechopen.99115*

#### **2.4 Sterile**

Sterile meningitis is defined by irritation of the meninges without the presence of pathological organism. In sterile meningitis the cause of meningeal irritation is usually SAH and circulating red blood cells in the subarachnoid space which can damage the arachnoid granulations and cause meningeal irritation. Clinically signs and symptoms of sterile meningitis are similar to bacterial meningitis in terms of neck stiffness, photophobia, nausea, vomiting and headaches, but leukocytosis or pyrexia are not accompanying the above-mentioned signs. Damage of the arachnoid granulations by the RBCs can cause non-resorptive hydrocephalus following a SAH or a traumatic brain injury with intracranial hemorrhage.

If sterile meningitis is suspected clinically then a LP is performed for CSF analysis. CSF analysis generally reveals elevated number of RBCs with normal or slightly elevated WBCs and normal protein and glucose content. It is important to mention that the protein and glucose content of the CSF can be affected by other factors but in general CSF analysis in sterile meningitis reveals elevated RBCs count. Treatment of sterile meningitis in mild cases is just symptomatic treatment for headaches, nausea and vomiting whereas in moderate to severe cases, CSF drainage is necessary to wash out the RBCs in the subarachnoid space and clear out the CSF. Lumbar drains for continuous CSF drainage are used if there are no contraindications. External ventricular drains (EVD) can be used to clear out the CSF if a lumbar drain is contraindicated or cannot be used for any reason.

If Sterile meningitis is not treated, non-resorptive hydrocephalus occurs due to the fact that RBCs damage the Pacchionian granulations and CSF reabsorption becomes impaired. In these cases, hydrocephalus is treated by placing a ventriculoperitoneal (V-P) shunt to divert the extra amount of CSF; if the abdominal cavity cannot be canulated due to ongoing inflammatory process or previous abdominal surgery and severe adhesions, then ventriculo-atrial or ventriculo-pleural shunts can be a substitution for the V-P shunt system.
