Cerebrospinal Fluid Mitochondrial Biomarkers in Ischemic Stroke and Alzheimer Disease

Inclusion Criteria: * Age 18 years or older. Patients treated at Xuanwu Hospital, Capital Medical University between March 2026 and May 2026. Diagnosis of ischemic stroke or Alzheimer disease according to standard clinical diagnostic criteria. Diagnostic lumbar puncture performed for clinical indications as part of routine medical care. Availability of residual cerebrospinal fluid after completion of clinically required testing. Ability to provide written informed consent, or availability of a legally authorized representative to provide consent when appropriate. For ischemic stroke patients, availability of baseline neurological assessment and planned follow-up for 90-day modified Rankin Scale assessment. Exclusion Criteria: * Lumbar puncture performed solely for research purposes rather than clinical indication. Insufficient residual cerebrospinal fluid volume for research flow cytometry analysis. Grossly bloody or severely contaminated cerebrospinal fluid sample that precludes reliable flow cytometry analysis. Known central nervous system infection, malignant meningitis, or other inflammatory or neoplastic condition that, in the investigator's judgment, may substantially confound cerebrospinal fluid mitochondrial measurements. Inability to obtain informed consent from the participant or legally authorized representative. Missing key clinical outcome data, including admission NIHSS, discharge NIHSS, or planned 90-day mRS follow-up for ischemic stroke participants. Any condition judged by the investigator to make the participant unsuitable for inclusion in the study.