eMedicine Specialties > Neurology > Neurological Infections

Subdural Empyema: Differential Diagnoses & Workup

Author: Segun T Dawodu, MD, JD, MBA, FAAPMR, FAANEM, CIME, DipMI(RCSed), Former Clinical Instructor, Mount Sinai Medical School; Current Director, Pain and Injuries Rehabilitation Services, PMRehab Pain and Sports Medicine Associates
Coauthor(s): Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Contributor Information and Disclosures

Updated: Mar 11, 2009

Differential Diagnoses

Acute Disseminated Encephalomyelitis
First Seizure in Adulthood: Diagnosis and Treatment
Acute Stroke Management
Haemophilus Meningitis
Aphasia
Headache: Pediatric Perspective
Benign Neonatal Convulsions
Herpes Simplex Encephalitis
Benign Positional Vertigo
Intracranial Epidural Abscess
Benign Skull Tumors
Intracranial Hemorrhage
Cardioembolic Stroke
Leptomeningeal Carcinomatosis
Cavernous Sinus Syndromes
Pseudotumor Cerebri
Cerebral Aneurysms
Subdural Hematoma
Cluster Headache
Tonic-Clonic Seizures
Complex Partial Seizures
Febrile Seizures

Other Problems to Be Considered

Acute necrotizing hemorrhagic leukoencephalopathy
Brain neoplasms
Cerebral thrombophlebitis
Confusional states and acute memory disorders
Cranial osteomyelitis
Endocarditis
Bacterial focal embolic encephalomalacia
Reactive subdural effusion
Abducens (VI) nerve palsy
Benign epilepsy syndromes

Workup

Laboratory Studies

  • CBC count may show a toxic leukocytosis.
  • Erythrocyte sedimentation rate (ESR) may be elevated.
  • Blood should be cultured for aerobic and anaerobic organisms.
  • Preoperative tests should include electrolytes, BUN, liver function tests, and CBC count if surgical intervention is being considered.

Imaging Studies

  • Cranial MRI is now the imaging study of choice, being superior to cranial CT scan in outlining the extent of subdural empyema and demonstrating the convexity and interhemispheric collections.
    • MRI also shows greater morphological detail than CT scan.
    • The sensitivity of MRI is improved by using gadolinium contrast medium.

      MRI scan of a subdural empyema in the left pariet...

      MRI scan of a subdural empyema in the left parietal area.

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      MRI scan of a subdural empyema in the left pariet...

      MRI scan of a subdural empyema in the left parietal area.

  • Cranial CT1 scan was the standard technique for quick diagnosis before the advent of MRI. The use of high-resolution, contrast-enhanced CT scan increases diagnostic yield, although it sometimes gives equivocal or normal results.
    • On CT scan, subdural empyema shows as a hypodense area over the hemisphere or along the falx; the margins are better delineated with the infusion of contrast material. Cerebral involvement also is visible.
    • Cranial osteomyelitis may be seen.
    • CT scan is the modality of choice if the patient is comatose or critically ill and MRI is not possible or is contraindicated.

      CT scan of a subdural empyema in the left tempora...

      CT scan of a subdural empyema in the left temporal/parietal area.

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      CT scan of a subdural empyema in the left tempora...

      CT scan of a subdural empyema in the left temporal/parietal area.

  • Cranial ultrasound2 has been helpful in differentiating subdural empyema from anechoic reactive subdural effusion in infants with meningitis accompanied by complex features (eg, increased echogenicity in the convexity collections, presence of hyperechoic fibrinous strands or thick hyperechoic inner membrane, and increases in echogenicity of the pia-arachnoid).

Other Tests

  • Preoperative - ECG, chest radiograph
  • Studies to define causes - Chest radiograph for pulmonary source, CT scan of paranasal sinuses and mastoid cells, sputum culture, nasal drip culture

Procedures

Lumbar puncture is currently contraindicated because of possible cerebral herniation from increased intracranial pressure.

  • Lumbar puncture may be performed in the course of a workup to rule out meningeal infection when increased intracranial pressure has been excluded.
  • CSF examination3 is an adjunctive test in the diagnosis of subdural empyema and may be obtained in addition to the other diagnostic tests previously outlined. CSF findings include the following:
    • WBC count (predominantly polymorphonuclear neutrophils) is increased. A significant increase (>50/µL) may be seen, although a slightly elevated cell count of 5-20/µL (reference range, 0-5/µL) does not rule out the possibility of subdural empyema.
    • Increased protein level greater than 100 mg/dL may be seen (reference range, 20-40 mg/dL), although less substantial elevations (50-90 mg/dL) do not rule out the possibility of subdural empyema.
    • Decreased glucose levels of 40 mg/dL or less usually are seen (reference range, 50-80 mg/dL). CSF glucose levels should be normalized with a blood glucose level obtained concurrently.
    • Occasionally, the CSF is normal and sterile in these cases.
    • The specific CSF findings should be compared with the accepted normal values of the treating physician's laboratory.

More on Subdural Empyema

Overview: Subdural Empyema
Differential Diagnoses & Workup: Subdural Empyema
Treatment & Medication: Subdural Empyema
Follow-up: Subdural Empyema
Multimedia: Subdural Empyema
References
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References

  1. Zimmerman RD, Leeds NE, Danziger A. Subdural empyema: CT findings. Radiology. Feb 1984;150(2):417-22. [Medline].

  2. Chen CY, Huang CC, Chang YC. Subdural empyema in 10 infants: US characteristics and clinical correlates. Radiology. Jun 1998;207(3):609-17. [Medline].

  3. Brennan MR. Subdural empyema. Am Fam Physician. Jan 1995;51(1):157-62. [Medline].

  4. Greenlee JE. Subdural empyema. In: Mandell GL, ed. Principles and Practice of Infectious Diseases. Vol 1. 4th ed. New York: Churchill;1994:900-903.

  5. Feuerman T, Wackym PA, Gade GF. Craniotomy improves outcome in subdural empyema. Surg Neurol. Aug 1989;32(2):105-10. [Medline].

  6. Sanford JP. Guide to antimicrobial therapy. Bethseda MD: Uniformed Services University Health Sciences. 1993;3.

  7. Delgado Tapia JA, Galera Lopez J, Santiago Martin J, et al. Subdural empyema due to Mycoplasma hominis after a cesarean section under spinal anesthesia. Rev Esp Anestesiol Reanim. 2005;52(4):239-242. [Medline].

  8. Dwarakanath S, Suri A, Mahapatra AK. Spontaneous subdural empyema in falciparum malaria: a case study. J Vector Borne Dis. Sep-Dec 2004;41(3-4):80-2. [Medline].

  9. Foerster BR, Thurnher MM, Malani PN, Petrou M, Carets-Zumelzu F, Sundgren PC. Intracranial infections: clinical and imaging characteristics. Acta Radiologica. October 2007;48(8):875-93. [Medline].

  10. Hall WA, Truwit CL. The surgical management of infections involving the cerebrum. Neurosurgery. February 2008;62 Supplement 2:519-30. [Medline].

  11. Krauss WE, McCormick PC. Infections of the dural spaces. Neurosurg Clin N Am. Apr 1992;3(2):421-33. [Medline].

  12. Mauser HW, Van Houwelingen HC, Tulleken CA. Factors affecting the outcome in subdural empyema. J Neurol Neurosurg Psychiatry. Sep 1987;50(9):1136-41. [Medline].

  13. Migirov L, Eyal A, Kronenberg J. Intracranial complications following mastoidectomy. Pediatr Neurosurg. Sep-Oct 2004;40(5):226-9. [Medline].

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Further Reading

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Keywords

subdural empyema, circumscript meningitis, cortical abscess, pachymeningitis interna, phlegmonous meningitis, purulent pachymeningitis, subdural abscess, SE, focal intracranial infections

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Contributor Information and Disclosures

Author

Segun T Dawodu, MD, JD, MBA, FAAPMR, FAANEM, CIME, DipMI(RCSed), Former Clinical Instructor, Mount Sinai Medical School; Current Director, Pain and Injuries Rehabilitation Services, PMRehab Pain and Sports Medicine Associates
Segun T Dawodu, MD, JD, MBA, FAAPMR, FAANEM, CIME, DipMI(RCSed) is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, American College of Sports Medicine, American Medical Association, American Medical Informatics Association, Association of Academic Physiatrists, International Society of Physical and Rehabilitation Medicine, and Royal College of Surgeons of England
Disclosure: Nothing to disclose.

Coauthor(s)

Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Nicholas Y Lorenzo, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Neurology
Disclosure: Nothing to disclose.

Medical Editor

Edward L Hogan, MD, Professor, Department of Neurology, Medical College of Georgia; Emeritus Professor and Chair, Department of Neurology, Medical University of South Carolina
Edward L Hogan, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, American Neurological Association, American Society for Biochemistry and Molecular Biology, Phi Beta Kappa, Sigma Xi, Society for Neuroscience, and Southern Clinical Neurological Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Florian P Thomas, MD, MA, PhD, Drmed, Director, Spinal Cord Injury Unit, St Louis Veterans Affairs Medical Center; Director, National MS Society Multiple Sclerosis Center; Professor, Department of Neurology and Psychiatry, Associate Professor, Institute for Molecular Virology, and Department of Molecular Microbiology and Immunology, St Louis University
Florian P Thomas, MD, MA, PhD, Drmed is a member of the following medical societies: American Academy of Neurology, American Paraplegia Society, and National Multiple Sclerosis Society
Disclosure: Nothing to disclose.

CME Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.

Chief Editor

Michael K Racke, MD, Professor of Neurology and Molecular Virology, Immunology, and Medical Genetics, Chairman of Neurology, Chief of Neurology Service, Ohio State University Medical Center
Michael K Racke, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, American Association for the Advancement of Science, American Association of Immunologists, and American Neurological Association
Disclosure: Teva Neuroscience Consulting fee Consulting; Peptimmune Inc. Consulting fee Consulting; Bristol Myers Squibb Consulting fee Consulting; EMD Serono Honoraria Speaking and teaching

 
 
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