A newborn with poor feeding, tongue fasciculations, and markedly reduced deep‑tendon reflexes—what should we tell the parents about prognosis and treatment?

Spinal Muscular Atrophy Type 1: Early Treatment is Critical

The correct answer is D: There is a new therapy that is more effective if started early. This newborn's presentation of tongue fasciculations, poor feeding, and decreased deep tendon reflexes is pathognomonic for spinal muscular atrophy (SMA) type 1, and disease-modifying therapies (nusinersen, onasemnogene abeparvovec, risdiplam) dramatically improve outcomes when initiated in the presymptomatic or early disease stages 1, 2, 3.

Why This Clinical Triad Confirms SMA Type 1

The combination of tongue fasciculations, hypotonia, and absent/decreased deep tendon reflexes in a newborn is pathognomonic for lower motor neuron disease, with SMA type 1 being the most common cause 1. This triad distinguishes peripheral (lower motor neuron) hypotonia from central causes 1.

• Tongue fasciculations are highly specific for lower motor neuron disease and appear as spontaneous discharges of entire motor units 4
• Decreased or absent deep tendon reflexes indicate lower motor neuron or peripheral nerve involvement 1, 4
• Poor feeding reflects progressive bulbar weakness characteristic of SMA type 1 5

Why Each Answer Option is Right or Wrong

Option A is Incorrect: This Condition is NOT Mild

SMA type 1 (Werdnig-Hoffmann disease) is the most severe form, with onset before 6 months of age 5. Without treatment, it causes:

• Severe progressive hypotonia and muscle weakness 5
• Respiratory failure predominating in intercostal muscles 5
• High mortality during the first 2 years of life 6
• Children never achieve the ability to sit unaided 5

Option B is Incorrect: Muscle Biopsy is NOT Needed

• Genetic testing with SMN1 gene analysis is the definitive diagnostic test 3
• The most common mutation is homozygous deletion of SMN1 exon 7, readily detected by PCR-based testing 3
• Muscle biopsy does not guide treatment selection—all three FDA-approved therapies target the same underlying SMN protein deficiency 3
• Immediate referral to pediatric neurology and genetics is essential for genetic confirmation 1

Option C is Incorrect: Nutrition Alone Does NOT Extend Life

While nutritional optimization through gastrostomy tube feeding may improve quality of life, it does not address the underlying motor neuron degeneration and will not extend life expectancy without disease-modifying therapy 1.

• Good nutrition alone cannot prevent respiratory failure or progressive motor neuron loss in untreated SMA type 1 1
• Feeding support addresses the symptom of poor feeding but not the progressive weakness 1
• Nutritional support should be viewed as an adjunct to, not a substitute for, disease-modifying therapy 1

Option D is Correct: Early Treatment Changes Outcomes

Three FDA-approved disease-modifying therapies are available 3:

1. Nusinersen (antisense oligonucleotide): Increases SMN protein by altering SMN2 splicing 3
2. Onasemnogene abeparvovec (gene therapy): Uses AAV9 vector to deliver functional SMN1 gene 3
3. Risdiplam (small molecule): Alters SMN2 splicing to increase functional SMN protein 3

These therapies significantly modify the natural course of disease when initiated early, before irreversible motor neuron loss occurs 2, 3. Newborn screening programs have demonstrated that treatment before symptom onset results in dramatically improved clinical outcomes 3.

Critical Action Steps

• Immediate referral to pediatric neurology and genetics for SMN1 genetic testing 1
• Do not delay treatment while awaiting confirmatory testing if clinical suspicion is high 3
• Initiate supportive care including respiratory monitoring and nutritional support as adjuncts to disease-modifying therapy 1
• Avoid attributing symptoms to "benign congenital hypotonia" without evaluating for tongue fasciculations and deep tendon reflexes, as this results in missed diagnosis 1

Common Pitfall

Focusing solely on feeding support without addressing the underlying neuromuscular disease represents inadequate care 1. The window for optimal treatment is narrow—motor neurons cannot be recovered once lost, making early diagnosis and treatment initiation paramount for survival and motor function 2, 3.