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Introduction:

Pial arteriovenous fistulas (AVFs) are rare spinal vascular anomalies with direct high-flow connections between arteries and veins, lacking a nidus. In some cases, they may mimic longitudinally extensive transverse myelitis (LETM) both clinically and radiologically.

Case Report:

A 69-year-old woman with hypertension, prediabetes, and hypercholesterolemia, but no prior neurological symptoms, presented with acute, rapidly progressive transverse myelopathy over 2–3 weeks, evolving to wheelchair dependence. She denied infections, systemic symptoms or recent vaccination.

On admission, one month after symptom onset, she had symmetric spastic paraparesis, T5 sensory level, apalesthesia in the lower limbs, brisk reflexes with bilateral Babinski and Hoffmann signs. Fluctuations in motor symptoms were noted during serial exams.

Spinal MRI revealed a longitudinally extensive, central T2 hyperintensity from T5 to the conus, with restricted diffusion and contrast enhancement. No flow voids or compression were observed.

Cerebrospinal fluid (CSF) analysis was inflammatory (26 leukocytes, protein 62 mg/dL, 2775 red blood cells), with a negative FilmArray panel. Given the fluctuation in symptoms and atypical features for autoimmune/inflammatory disease, angiography was performed prior to corticosteroid use and revealed a pial AVF at T10. Anti-aquaporin4 and anti-MOG results were negative and a type 4 oligoclonal band pattern was observed. 

Discussion:

Pial AVFs can cause venous hypertension and spinal cord ischemia, mimicking LETM and even producing inflammatory CSF findings due to blood–spinal cord barrier disruption. Differentiating these conditions is critical, as treatments diverge significantly. Corticosteroids, commonly used in inflammatory myelitis, may worsen venous congestion in AVFs.

In this case, the patient’s age, symptom fluctuation, and absence of progressive deterioration at admission raised suspicion for AVF. Early angiography confirmed the diagnosis, avoiding potentially harmful immunosuppression.