SUMMARY
# Sporadic ALS Initiation Biology: Deep Phenotyping of At-Risk Cohorts
## Background and Rationale
Sporadic amyotrophic lateral sclerosis (ALS) accounts for approximately 90% of cases, yet the biological triggers initiating motor neuron degeneration in genetically predisposed individuals remain poorly understood. This longitudinal clinical study employs comprehensive deep phenotyping of at-risk cohorts to identify the earliest molecular and cellular events preceding clinical symptom onset. The e
METHODOLOGY NOTES
# Sporadic ALS Initiation Biology: Deep Phenotyping Protocol
## Phase 1: Cohort Recruitment and Baseline Characterization (Months 1-12)
**Participant Selection and Stratification**: Recruit 500 at-risk individuals (age 40-75) meeting criteria: (1) first-degree relatives of sALS patients (n=200), (2) occupational/environmental exposure history (n=150), (3) subclinical neurophysiological abnormalities on screening electromyography (n=100), (4) elevated serum phosphorylated tau or neurofilament light chain (>75th percentile; n=50). Enroll 300 age-matched, exposure-matched controls. Perform comprehensive clinical assessments including ALS Functional Rating Scale-Revised (ALSFRS-R), Medical Research Council grading, quantitative grip strength dynamometry, and detailed occupational/environmental exposure questionnaires.
## Phase 2: Multi-Modal Deep Phenotyping (Months 3-24)
**Neuroimaging Protocol**: Conduct 3T MRI brain and spinal cord imaging with quantitative T2 relaxometry, diffusion t