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Testing & Diagnosis

Lumbar puncture

Quick answer

A spinal fluid sample can measure amyloid and tau directly and evaluate for inflammation or infection.

Author:
Illinois Dementia Guide editorial team
Medically reviewed by:
Amarish Dave, DO, Board Certified Neurologist
Published:
August 2026
Last medically reviewed:
August 2026
Geographic relevance:
Illinois, United States

Overview

The procedure takes about 20 to 30 minutes in an outpatient setting, using local anesthetic. It is a well-established option when biomarker confirmation is needed.

When it is used

  • Biomarker confirmation when PET is unavailable or not covered
  • Atypical, rapidly progressive, or younger-onset presentations
  • Suspicion of inflammatory or infectious causes

Risks and preparation

  • Post-procedure headache in a minority of patients
  • Blood thinners may need to be held under medical guidance
  • Plan for a ride home and a quiet day afterward

Medically reviewed. Last reviewed August 2026. This page is educational information, not individualized medical advice.

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