PMC10434843_01
Patients flow cytometry supports MMN-like diagnosis. Projection of the immunoglobulin (Ig) CSF/Ig serum index compared to the albumin CSF/albumin serum index at the time of sample collection. (a) Reiber scheme for IgG, IgM, and IgA. The red dots indicate the calculated quotient. The albumin quotient indicates a blood-CSF barrier dysfunction. (b) Selected flow cytometry parameters in percent (Supplemental Figure 2 for gating scheme) of peripheral blood and CSF compared to patients with inflammatory neuropathy and non-inflammatory control patients. Red dot indicates the anti-CASPR2 + MMN-like patients (CR) values. Light blue dots depict values of 39 age-matched non-inflammatory controls [i.e. somatoform disorder patients (SD)with no signs indicating an inflammatory CSF]. Dark blue dots depict 11 age-matched inflammatory neuropathy patients [7x chronic inflammatory demyelinating polyneuropathy (CIDP), 2x multifocal motor neuropathy (MMN), and 2x Guillain-Barre syndrome (GBS)] for comparison. Line and error bars depict mean + standard deviation.. CASPR2, contactin-associated protein 2; CSF, cerebrospinal fluid; MMN-like, motor neuropathy-like.
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A diagnostic lumbar puncture and subsequent cerebrospinal fluid (CSF) analysis showed a normal cell count and slightly increased total protein levels (603 mg/l) with a blood-CSF barrier dysfunction as quantified by the albumin quotient, but no intrathecal immunoglobulin synthesis (Figure 1). Flow cytometry analysis revealed an increase of activated HLA-DR expressing CD4+ T cells (33.7%) in the CSF compared to age-matched non-inflammatory controls [Figure 1(b)].
Ultrasonography shows enlargement of peripheral nerves. Ultrasonography of peripheral nerves in the right (a, c, e) and left (b, d, f) arm. Enlargement of right median nerve (rMN) in the proximal (a) and middle (c) upper arm compared to the left median nerve (lMN) (b, d). Enlargement of fascicles of the right (e) ulnar nerve (rUN) in the proximal upper arm compared to the left ulnar nerve (lUN) (f). Ultrasound depth depicted as a scale on the right, cross-sectional area (CSA) of the respective nerve on the bottom left. Circled area depicts the measured nerve.
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We diagnosed a MMN as the patient fulfilled the diagnostic criteria.   A peripheral nerve ultrasonography (Figure 2) showed an enlargement of the cross-sectional areas of the right median nerve and discontinuous swelling of individual fascicles of the right median and ulnar nerve in the upper arm supporting the MMN-like phenotype.