Do my symptoms of left arm weakness, particularly in digits 4 and 5, muscle fatigue in forearms, and difficulty holding my child on the left side, given my history of benign fasciculations syndrome (BFS) and recent illnesses, suggest a low likelihood of amyotrophic lateral sclerosis (ALS) in a 43-year-old female?

Your Symptoms Point Away from ALS

Your presentation is highly inconsistent with ALS and strongly suggests a benign process, particularly given your established diagnosis of benign fasciculation syndrome (BFS), the acute onset of symptoms following recent illnesses, and the pattern of weakness affecting specific digits rather than the progressive, diffuse pattern typical of ALS.

Why This is NOT ALS

Temporal Pattern Argues Against ALS

• ALS does not present with symptom onset over days to weeks 1. The American Academy of Neurology notes that symptom onset in less than 24 hours suggests stroke or other acute process, and your 2-3 week timeline is far too rapid for typical ALS progression 1.

• Your symptoms began immediately following multiple systemic illnesses (shingles, gastroenteritis, and another illness), which is not characteristic of ALS but is consistent with post-viral fatigue, deconditioning, or inflammatory processes 1.

Your BFS Diagnosis is Highly Reassuring

• BFS has an excellent prognosis with essentially no progression to ALS 2, 3. A systematic review of 180 BFS patients followed over months to years found that 98.3% had persistent fasciculations, but zero patients developed motor neuron dysfunction 3.

• Even when BFS patients show minor chronic neurogenic changes on EMG, they do not progress to ALS 2. In a follow-up study with median 6.5 years of observation, all patients with baseline EMG abnormalities remained stable, and two-thirds reported symptomatic improvement 2.

• Your 6-year history of BFS without developing true weakness or atrophy is incompatible with ALS, which would have declared itself definitively by now 2, 3.

Pattern of Weakness is Wrong for ALS

• ALS typically presents with progressive, asymmetric but eventually diffuse weakness, not isolated digit involvement 1. Your specific complaint about digits 4 and 5 (ulnar distribution) suggests a peripheral nerve issue, not motor neuron disease.

• The American Academy of Neurology emphasizes that ALS presents with limb-onset in 65-75% of cases, manifesting as progressive muscle weakness in arms or legs with associated atrophy 1. You describe subjective weakness and fatigue without objective atrophy.

• True ALS weakness is accompanied by visible muscle wasting, fasciculations in multiple body regions, and abnormal reflexes (either hyperreflexia from upper motor neuron involvement or hyporeflexia from lower motor neuron loss) 1, 4.

Your Symptoms Suggest Alternative Explanations

• Ulnar nerve compression or neuropathy is far more likely given the specific involvement of digits 4 and 5, especially if you've been positioning your arm differently while ill or deconditioned 4.

• Post-viral fatigue and deconditioning after your recent illnesses (shingles, gastroenteritis) commonly cause subjective weakness, muscle fatigue with typing, and difficulty with previously easy tasks like holding your child 1.

• Anxiety and health anxiety are strongly associated with BFS 5. Healthcare workers with BFS show 60% prevalence of anxiety (often severe) and 33% prevalence of depression, with five-fold increased risk of BFS when these conditions are present 5.

What You Should Do

Immediate Steps

• Schedule evaluation with your neurologist to document objective strength testing, reflexes, and presence or absence of muscle atrophy 4.

• Request EMG/nerve conduction studies if not recently performed 4, 6. These are mandatory for detecting lower motor neuron degeneration and can identify ulnar neuropathy or other peripheral nerve issues 4.

• Consider nerve conduction studies focused on the ulnar nerve given your specific digit 4-5 involvement 6.

Clinical Monitoring

• The American Academy of Neurology recommends that progression to maximum disability after more than 4 weeks should prompt consideration of diagnoses other than acute processes 1. If your symptoms stabilize or improve over the next few weeks, this further confirms a benign etiology.

• Watch for objective signs that would suggest ALS: visible muscle wasting, fasciculations spreading to multiple body regions, difficulty with fine motor tasks beyond fatigue, slurred speech, or swallowing difficulties 1, 4.

Address Contributing Factors

• Recognize that anxiety about ALS is extremely common in BFS patients and can amplify symptom perception 5. The fear of having ALS plays an important role in BFS, especially among those with medical knowledge 5.

• Post-viral recovery takes time. Your recent shingles and gastrointestinal illnesses can cause prolonged fatigue and subjective weakness that resolves gradually 1.

Critical Reassurance Points

• BFS patients followed for years show fasciculations persist in 98.3% but improvement in symptoms occurs in 51.7% 3. Your fasciculations continuing is expected and does not indicate progression.

• The median survival of ALS is 3-5 years from symptom onset 1. Your 6-year history of fasciculations without developing the hallmark features of ALS (progressive weakness with atrophy, bulbar symptoms, respiratory decline) makes ALS extraordinarily unlikely.

• Up to 10% of patients initially suspected of having ALS actually have a mimic disorder 4. Your acute presentation following illnesses, specific ulnar distribution, and established BFS diagnosis place you firmly in the "not ALS" category.