T

Clinical Features to Aid in the Diagnosis of Acute Flaccid Myelitis versus Transverse Myelitis

Alfred Balasa M.D., Nikita M. Shukla M.D, Timothy E. Lotze M.D.Pediatric Neurology and Developmental Neuroscience, Baylor College of Medicine, Houston, Texas, USA

Median age in the AFM cohort was 5.5 years (SD ± 2 years) and 10.5 years (SD ± 2 years) for the TM cohort. 78% were female in the AFM cohort and 63% were female in the TM cohort.

78% of AFM patients had viral symptoms and fever preceding the onset of neurologic symptoms compared to 44% of TM patients. 56% of AFM patients reported neck or extremity pain preceding the onset of weakness compared to 31% of TM patients.

57% of AFM patients had isolated upper extremity (UE) weakness while 43% had involvement of both the UE and lower extremities (LE). None of the AFM patients had isolated LE weakness. Of the AFM patients with UE and LE involvement, 86% had asymmetric weakness. 44% of the TM patients had isolated LE involvement while 44% had both UE and LE involvement. Only 12% had isolated UE involvement. Of the TM patients with UE and LE involvement, 66% had symmetric weakness.

Urinary symptoms were present in 14% of the AFM patients and 31% of the TM patients. Similarly, only 14% of patients with AFM reported paresthesia and none reported other sensory symptoms. In comparison, 47% of TM patients reported sensory symptoms, such as numbness, tingling, or a sensory level.

Results

Illness Age (yrs) Female (%) Male (%)

AFM 5.5 (SD ± 2) 78 22

TM 10.5 (SD ± 2) 63 27

Table 1: Patient characteristics. AFM – acute flaccid myelitis, TM –Transverse myelitis

IllnessViral

prodrome(%)

Neck or extremity pain

(%)

Urinary symptoms

(%)Paresthesia

(%)

AFM 78 56 14 14

TM 44 31 31 47

Illness Isolated upper

extremity weakness (%)

Isolated lower extremity weakness

(%)

Upper and lower extremity weakness

(%)

Symmetric weakness

(%)

Asymmetric weakness

(%)

AFM 57 0 43 14 86

TM 12 44 44 66 34

Table 2: Percentage of viral prodrome, pain, urinary symptoms and paresthesia.

Table 3: Characteristics of muscle weakness at presentation.

Acute flaccid myelitis (AFM) is characterized by sudden onset of flaccid paralysis in one or more limbs with MRI showing involvement primarily of the central gray matter. In the acute phase, spinal cord imaging can appear similar to that seen in transverse myelitis (TM). Thus, clinical features that help distinguish the two disease processes are necessary for appropriate diagnosis, treatment, and prognosis. The aim of our study was to outline clinical features that may help distinguish between AFM and TM.

Background

In conclusion, evaluation of our cohort of AFM and TM patients suggests that AFM patients are more likely to present with a preceding fever and viral illness prior to their neurologic symptoms. They are also more likely to present with isolated UE involvement with neck or extremity pain preceding the onset of weakness. Other sensory symptoms such as numbness and tingling do not seem to be a predominant part of the presentation of AFM. Urinary symptoms are also more common in the TM population. Consideration of these clinical differences may help expedite diagnosis, therefore guiding management to improve clinical outcomes.

Conclusion

Figure 1: Number of AFM in the USA by state in 2018 (cdc.gov)

2018 confirmed cases of acute flaccid myelitis (AFM) by state(N = 235)

Figure 2: Cases of AFM by month in the USA (cdc.gov)

Number of confirmed U.S. AFM cases reported to CDC by month of onset(August 2014 – May 2019)

Retrospective chart review was performed of the nine patients presenting to Texas Children’s Hospital diagnosed with AFM (2018-19) and 32 patients diagnosed with TM (2010-18).

Methods