Outcomes of Colorado children with acute flaccid myelitis at 1 year

Abstract

Objective: We describe long-term functional, neurodiagnostic, and psychosocial outcomes of a cohort of 12 children from Colorado diagnosed with acute flaccid myelitis (AFM) in 2014.

Methods: Children were assessed every 3 months for 1 year or until clinical resolution. Assessments included neurologic examination, MRI, EMG/nerve conduction studies (NCS), functional measures (Assisting Hand Assessment, Hammersmith Functional Motor Scale), and Patient-Reported Outcomes Measurement Information System questionnaires.

Results: Eight of 12 children completed the study. Six of 8 had persistent motor deficits at 1 year; 2 demonstrated full recovery. Four were not enrolled, 2 of whom reported full recovery. The 6 affected were weakest in proximal muscles, showing minimal to no improvement and significant atrophy at 1 year. All patients improved in distal muscle groups. Cranial nerve dysfunction resolved in 2 of 5 and improved in all. Four of 5 showed progressive functional improvement at 6 and 12 months. Two of 8 reported pain at 1 year. Three of 8 reported depressive symptoms. Repeat MRI was performed in 7 of 8 children a median of 7 months after onset and showed significant improvement or normalization in all but one child. Repeat EMG/NCS was performed on 4 children a median of 8 months after onset and showed ongoing denervation and chronic reinnervation in 3 children with persistent deficits.

Conclusions: At 1 year, children with AFM demonstrated functional gains but weakness persisted. EMG changes correlated with persistent deficits better than imaging. Despite improvements, AFM had substantial long-term functional effects on affected children.

Figure 1. Study inclusion chart

AFM = acute flaccid myelitis; CHCO = Children's Hospital Colorado.

Figure 2. Kaplan-Meier plot of time to neurologic recovery

All 12 patients with acute flaccid myelitis in the Children's Hospital Colorado cluster are included in this analysis. Two patients were lost to follow-up after initial presentation and were censored at time 0. One patient who was not enrolled in the study reported full recovery via telephone interview at 1 month and another patient who was not enrolled in the study was noted to have full functional recovery at follow-up neurologic clinic visit at 2 months.

Figure 3. Muscle atrophy of affected limbs in children with acute flaccid myelitis (AFM)

(A) Patient 5, 8 months after onset of symptoms with atrophy of the left proximal upper extremity and shoulder girdle. (B) Patient 11, 11 months after onset of symptoms with atrophy of the proximal left arm and chest. (C) Patient 1, 6 months after onset of symptoms with inability to raise the affected left arm. (D) Two-year-old patient with AFM 1.5 years after onset of symptoms in 2013 with persistent asymmetric atrophy of the affected right leg and inability to bear weight.

Figure 4. Strength and self-reported function of most affected upper and lower extremity in children with acute flaccid myelitis over 1 year

(A) Spaghetti plot of Medical Research Council (MRC) strength score of patients' most affected upper extremity muscle at onset and 3, 6, and 12 months follow-up, revealing little to no change in strength in the most affected extremity at 1 year. (B) Spaghetti plot shows Patient-Reported Outcomes Measurement Information System (PROMIS) scores for upper extremity function at 3, 6, and 12 months follow-up. Mean score is 50 with 1 SD = 10 points. Initially, 6 patients were greater than 1 SD below the mean. This improved to 3 patients >1 SD below the mean at 1 year. (C) Spaghetti plot shows MRC strength score of patients' most affected lower extremity muscle at onset and 3, 6, and 12 months follow-up, showing improvement in strength in all 3 patients with lower extremity weakness. (D) Spaghetti plot shows PROIMS scores for mobility function at 3, 6, and 12 months follow-up. Mean score is 50 with 1 SD = 10 points.