Central Nerve System Infections

Central Nerve System Infections

Central nervous system infections of interest to neurosurgeons in­clude those that cause focal neurologic deficit due to mass effect, require surgical aspiration or drainage because antibiotic therapy alone is insufficient, cause mechanical instability of the spine, or occur after neurosurgical procedures.

Cranial Infections -1


 The skull is highly vascular and resistant to infections. osteomyelitis of the skull may develop by contiguous spread from pyogenic sinus disease or from contamination by penetrating trauma.
Staphylococcus aureus and S. epidermidis are the most frequent  causative organisms. Patients usually present with redness, swelling, and pain. Contrast head CT aids diagnosis and shows the extent of involved bone, along with associated abscesses or empyema. Os­teomyelitis treatment entails surgical debridement of involved bone followed by 2 to 4 months of antibiotics. Craniotomy wound infec­tions are a special concern because performing a craniotomy creates a devascularized free bone flap susceptible to infection and not pen­etrated by antibiotics. These wounds must be debrided and the bone
 flaps removed and discarded. Subsequent care involves appropriate antibiotic therapy, observation for signs of recurrent infection off antibiotics, and return to the OR for titanium or methyl methacrylate cranioplasty 6 to 12 months later

Subdural Empyema

Subdural empyema is a rapidly progressive pyogenic infection. The subdural space lacks significant barriers to the spread of the infection, such as compartmentalization or septations. Subdural empyema usually occurs over the cerebral convexities. Potential infectious sources include sinus disease, penetrating trauma, and otitis. Streptococci and staphylococci are the most frequently found organisms. Presenting symptoms include fever, headache, neck stiffness, seizures, or focal neurologic deficit. Neurologic deficit re­sults from inflammation of cortical blood vessels, leading to throm­bosis and stroke. The most common deficit is contralateral hemi­paresis. Patients with suggestive symptoms should undergo rapid contrast CT scan. Lumbar puncture frequently fails to yield the of­fending organism and risks herniation due to mass effect. typical treatment is wide hemicraniectomy, dural opening, and lavage. The pus may be thick or septated, making burr hole drainage or small craniotomy insufficient. Patients then require I to 2 months of an­ tibiotics. Subdural empyema has 10 to 20% mortality and common chronic sequelae, including seizure disorder and residual hemipare­sis. However, many patients make a good recovery

Brain Abscess

Brain abscess is encapsulated infection within the brain parenchyma. It may spread hematogenously in patients with endocarditis or intracardiac or intrapulmonary right-to-left shunts, by migration from the sinuses or ear, or via direct seeding by pene­trating trauma. Disorganized cerebritis often precedes formation of the organized, walled-off abscess. Patients may present with non­ specific symptoms such as headache, nausea, or lethargy. or with focal neurologic deficit such as hemiparesis. Alternatively, patients may present in extremis if the abscess ruptures into the ventricu­lar system. Abscesses appear as well-demarcated, ring-enbancing,
thin-walled lesions on CT scan and MRl, and often have associated edema and mass effect. Patients require antibiotic therapy after needle aspiration or surgical evacuation. Antibiotic therapy with­out surgical evacuation may be considered for patients with small, multiple, or critically located abscesses. Abscesses that cause mass effect, decreased mental status, are large, or that fail to decrease in size after a week of antibiotics, should be evacuated. Nonsurgical management still requires aspiration or biopsy for organism cul­ture and sensitivities. Blood and CSF cultures rarely give definitive diagnosis. Removal of an encapsulated abscess significantly short­ ens the length of antibiotic therapy required to eliminate all organ­ isms. Common chronic sequelae after successful treatment include seizures or focal neurologic deficit

Spine Infections -2

Pyogenic Vertebral Osteomyelitis

Pyogenic vertebral osteomyelitis is a destructive bacterial infection of the vertebrae, usually of the vertebral body. Vertebral osteomyelitis frequently results from hematogenous spread of dis­tant disease, but may occur as an extension of adjacent disease, such as psoas abscess or perinephric abscess. S. aureus and Enterobac­ter spp. are the most frequent etiologic organisms. Patients usually present with fever and back pain. Diabetics, IV drug abusers, and dialysis patients have increased incidence of vertebral osteomyeli­tis. Epidural extension may lead to compression of the spinal cord or nerve roots with resultant neurologic deficit. Osteomyelitis presents a lytic picture on imaging and must be distinguished from neoplastic disease. Adjacent intervertebral disc involvement occurs frequently with pyogenic osteomyelitis. but rarely with neoplasia. Plain films and CT help assess the extent of bony destruction or deformity such as kyphosis. MRI shows adjacent soft tissue or epidural dis­ease. Most cases can be treated successfully with antibiotics alone, although the organism must be isolated to steer antibiotic choice. Blood cultures may be positive. Surgical intervention may be re­quired for debridement when antibiotics alone fail, or for stabiliza­tion and fusion in the setting of instability and deformity

Tuberculous Vertebral Osteomyelitis

Tuberculous vertebral osteomyelitis, also known as Pott's disease, occurs most commonly in underdeveloped countries and in immunocompromised people. Several features differentiate tuber­culous osteomyelitis from bacterial osteomyelitis. The infection is indolent and symptoms often progress slowly over months. Tuber­culosis rarely involves the intervertebral disc. The involved bodies may have sclerotic rather than lytic changes. Multiple nonadjacent vertebrae may be involved. Diagnosis requires documentation of acid-fast bacilli. Treatment involves long-term anti mycobacterial drugs. Patients with spinal instability or neural compression from epidural inflammatory tissue should undergo debridement and fu­sion as needed


Primary infection of the intervertebral disc space, or discitis, is most commonly secondary to postoperative infections. Spontaneous discitis occurs more commonly in children. S. epidermidis and S. aureus account for most cases. The primary symptom is back pain. Other signs and symptoms include radicular pain, fevers, paraspinal muscle spasm, and localized tenderness to palpation. Many cases will resolve without antibiotics. Antibiotics are generally given for positive blood or biopsy cultures or persistent constitutional symp­toms. Most patients will have spontaneous fusion across the involved disc and do not need debridement or fusion

Epidural Abscess

Epidural abscesses may arise from or spread to the adjacent bone or disc, so distinguishing between vertebral osteomyelitis or discitis and a spinal epidural abscess may be difficult. The most common presenting signs and symptoms are back pain, fever, and tenderness to palpation of the spine. The most significant risk of epidural ab­scess is weakness progressing to paralysis due to spinal cord or nerve root damage. Cord and root damage may be due to direct compres­sion or to inflammatory thrombosis resulting in venous infarction. S. aureus and Streptococcus spp. are the most common organisms. The source may be hematogenous spread, local extension, or oper­ative contamination. MRI best demonstrates the epidural space and degree of neural compromise. Patients with suspected spinal epidu­ral abscess should undergo surgical debridement for decompression and diagnosis, followed by culture-directed antibiotic therapy. Rel­ative contraindication, to surgery include prohibitive comorbidities or total lack of neurologic function below the involved level. Pa­tients with no neurologic deficits and an identified organism may be treated with antibiotics alone and very close observation. This is controversial, however, because these patients can undergo rapid and irreversible neurologic decline. Most epidural abscesses can be accessed via laminectomy without fusion. Collections predomi­nantly anterior to the cervical or thoracic cord may require anterior approach and fusion.


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