Spinal epidural abscess (SEA) was first described in the medical literature in 1761 and represents a severe, generally pyogenic infection of the epidural space requiring emergent neurosurgical intervention to avoid permanent neurologic deficits. Spinal epidural abscess comprises 0.2 to 2 cases per 10,000 hospital admissions. This review intends to offer detailed evaluation and a comprehensive meta-analysis of the international literature on SEA between 1954 and 1997, especially of patients who developed it following anesthetic procedures in the spinal canal. In this period, 915 cases of SEA were published. This review is the most comprehensive literature analysis on SEA to date. Most cases of SEA occur in patients aged 30 to 60 years, but the youngest patient was only 10 days old and the oldest was 87. The ratio of men to women was 1:0.56. The most common risk factor was diabetes mellitus, followed by trauma, intravenous drug abuse, and alcoholism. Epidural anesthesia or analgesia had been performed in 5.5% of the patients with SEA. Skin abscesses and furuncles were the most common source of infection. Of the patients, 71% had back pain as the initial symptom and 66% had fever. The second stage of radicular irritation is followed by the third stage, with beginning neurological deficit including muscle weakness and sphincter incontinence as well as sensory deficits. Paralysis (the fourth stage) affected only 34% of the patients. The average leukocyte count was 15,700/µl (range 1,500–42,000/µl), and the average erythrocyte sedimentation rate was 77 mm in the first hour (range 2–50 mm). Spinal epidural abscess is primarily a bacterial infection, and the gram-positive Staphylococcus aureus is its most common causative agent. This is true also for patients who develop SEA following spinal anesthetics. Magnetic resonance imaging (MRI) displays the greatest diagnostic accuracy and is the method of first choice in the diagnostic process. Myelography, commonly used previously to diagnose SEA, is no longer recommended. Lumbar puncture to determine cerebrospinal fluid protein concentrations is not needed for diagnosis and entails the risk of spreading bacteria into the subarachnoid space with consequent meningitis; therefore, it should not be performed. The therapeutic method of choice is laminectomy combined with antibiotics. Conservative treatment alone is justifiable only for specific indications. Laminotomy is a therapeutic alternative for children. The mortality of SEA dropped from 34% in the period of 1954–1960 to 15% in 1991–1997. At the beginning of the twentieth century, almost all patients with SEA died. Parallel to improvements in the mortality rate, today more patients experience complete recovery from SEA. The prognosis of patients who develop SEA following epidural anesthesia or analgesia is not better than that of patients with noniatrogenic SEA, and the mortality rate is also comparable. The essential problem of SEA lies in the necessity of early diagnosis, because only timely treatment is able to avoid or reduce permanent neurologic deficits.

Spinal epidural abscess: a meta-analysis of 915 patients.

Narcotics reduce the behavioral response to injury, while leaving unaffected the response to other stimuli. This effect could be due to a reduction of the central transmission of injury signals (modulation of sensory throughput) or to an effect on higher inte~ative levels concerned with stimulus recognition or stimulus interpretation ** . Since much of the functional capacity of the central nervous system and nearly every level of the neuraxis is involved in signal processing, observations limited to the effect of systemically administered narcotics on behavior will provide little information regarding the specific sites and mechanisms of action of narcotic analgetics. Investigators interested in these aspects of narcotic activity have therefore resorted to experimental approaches which permit a detailed study of the interaction between narcotic analgetics and particular regions and/or functional systems within the central nervous system. Recording of local electrical activity following systemic application of a narcotic does not specify where the narcotic is acting. Similarly local lesions or electrical stimulation can only indicate through which systems narcotics may act and do not reveal the causal chain between injury and pain. As a consequence of the inadequacies of these approaches, investigators have turned with increasing frequency to methods which permit the application of drugs directly to single neurons or circumscribed neuronal pools. The mi~roiontophoretic technic has provided much of our limited information concerning the direct effects of narcotic analgetics on neuronal activity. ~n~o~unately, the microiontophoretic stimulation of a single neuron usually is incapable of eliciting a detectable behavioral response. Therefore, even though many neurons can be tested for their individual sensitivities to suspected neurotransmitter or other agents, it cannot be determined by ionto-

Narcotic analgetics: CNS sites and mechanisms of action as revealed by intracerebral injection techniques

The concept of a barrier between blood, on the one hand, and the brain on the other derives from the classical studies of Ehrlich and of Goldmann on vital staining; it was noted that a large variety of acid dyes, of which trypan blue was one, would pass out of the blood into the tissues of the body making them voloured; the brain and spinal cord stood out in contrast to the rest of the tissues in that, with the exception of highly localized regions, such as the area postrema, they remained unstained. In the thirties and forties of this century some doubt was cast on this concept of a barrier between blood and brain; thus King in 1938 (1) argued that the essential phenomenon was one of failure to stain, and this could have been due to the absence of suitable connective tissue to take up the stain.

The Blood Brain Barrier

Thirty-five cases of spinal epidural abscess were evaluated retrospectively and compared with 153 cases reported in the literature. As in other series, Staphylococcus aureus was the major pathogen. Patients with acute abscesses had fever, leukocytosis, and purulence at surgery. Patients with chronic abscesses had less fever and leukocytosis, more granulation tissue at surgery, and a greater delay in diagnosis but retained the potential for rapid neurologic deterioration. In contrast to other studies, abscesses in both the lumbar and anterior spinal compartments and patients with specific sources of infection occurred with greater frequency. Myelography was the diagnostic method of choice. Only four of nine patients had diagnostic computed tomography. Earlier diagnosis and treatment led to a significant improvement in outcome. Both steroid administration and greater neurologic impairment adversely affected outcome. Neurologic improvement following surgery was dependent on the duration of the deficit. A combination of antibiotics and surgical drainage remains the treatment of choice.

Update of Spinal Epidural Abscess: 35 Cases and Review of the Literature

The incidence of infectious maxillary sinusitis (IMS) and its clinical relevance was prospectively studied in 162 consecutive critically ill patients who were mechanically ventilated for a period longer than 7 d. All had a paranasal computed tomographic (CT) scan within 48 h of admission and were divided into three groups according to the radiologic aspect of their maxillary sinuses: Group 1 = normal maxillary sinuses (n = 40), Group 2 = maxillary mucosal thickening (n = 26), Group 3 = radiologic maxillary sinusitis (RMS) defined as the presence of an air fluid level and/or opacification of maxillary sinuses (n = 96). Group 1 patients were randomized between nasal and oral endotracheal intubation with a gastric intubation performed via the same route and had a second paranasal CT scan 7 d later. Endotracheal and gastric tubes were left in their original position in Group 2 patients and a second paranasal CT scan was performed 7 d later. All patients of Group 3 underwent a transnasal puncture for bacteriologic analysis of maxillary sinus content. Forty-five spontaneously breathing patients served as a control group. In all patients with RMS, the occurrence of bronchopneumonia (BPN) was prospectively assessed for 7 d following the initial CT scan. Upon inclusion, only 25% of the patients had normal maxillary sinuses whereas all patients in the control group had normal paranasal CT scans. After 7 d, 46% of Group 2 patients had evidence of RMS. Risk factors for RMS were nasal placement and duration of endotracheal and gastric intubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk factors and clinical relevance of nosocomial maxillary sinusitis in the critically ill.

Intraoperative intercostal nerve freezing to prevent postthoracotomy pain.

Neurological complications of infections of head and neck.

A neuropsychological battery was given to a CT-defined group of children shunted for uncomplicated hydrocephalus with estimated normal range IQs. When no other brain anomalies were present, verbal IQ estimates were inferior to age and sex matched controls, but still in the normal range. In the presence of average academic performance and normal range IQ, impairment of neuropsychological functioning in verbal and nonverbal memory, fine motor speed, and visuospatial problem solving was observed. Successful neurosurgical management of hydrocephalus is not necessarily equated with achieving normal neuropsychological functioning.

Neuropsychological Functioning in Children with Shunted Uncomplicated Hydrocephalus

Spinal epidural abscess represents a surgical emergency because it rapidly leads to complete paralysis below the lesion. Early surgical drainage is essential to complete recovery. A review of the 46 cases in children reported in the English literature indicates that the sequence of first symptoms (fever, localized back pain, and radicular pain) should afford early diagnosis in most cases. Staphylococci are the most frequent bacteriologic invaders.

Ralph J. Kaplan

Papers

Intraoperative intercostal nerve freezing to prevent postthoracotomy pain.

Neurological complications of infections of head and neck.

Neuropsychological Functioning in Children with Shunted Uncomplicated Hydrocephalus

Spinal Epidural Abscess in Children Early Diagnosis and Immediate Surgical Drainage Is Essential To Forestall Paralysis

Diffusion of non-electrolytes in brain tissue.