Peripheral neuropathy in Krabbe disease: electrodiagnostic findings.

BACKGROUND

Krabbe disease (KD) is associated with marked central and peripheral demyelination and nerve conduction studies (NCS) typically show a mixed sensorimotor demyelinating peripheral neuropathy (PN).

OBJECTIVES

To further characterize the PN in a large cohort of patients with KD and to assess the diagnostic sensitivity of NCS in this condition.

METHODS

The authors report the results of electrodiagnostic studies performed in 27 children with KD, ranging in age from 1 day to 8 years, whose diagnosis was confirmed by leukocyte lysosomal enzyme analysis.

RESULTS

Based on age-adjusted normative values, 25 of 27 patients had abnormal NCS (sensitivity > 90%) when at least one motor and one sensory nerve were tested in a lower and an upper extremity. Of the 24 patients with the early infantile form of the disease, 23 had abnormal NCS (sensitivity > 95%). Abnormal sural sensory responses (SNR) (82%), F-wave latencies (FWL) (85%), motor conduction velocities (CV) (82%), and distal motor latencies (DL) (76%) were the most sensitive indices. In the lower extremities the sensitivity of motor CV, FWL, and motor DL was 79%, 79%, and 57%, respectively, while in the upper limbs the corresponding sensitivities were 80%, 87%, and 73%. No conduction block was detected and there was uniform slowing of CV. SNR was unobtainable or abnormal in 82% of patients. The compound muscle action potential amplitudes were within normal limits in >70% of lower limb and >45% of upper limb responses. Marked NCS abnormalities were found in a 1-day-old and two 3-week-old neonates, the youngest patients reported to date. NCS were abnormal in 5/9 children with normal EEG or evoked potentials. The severity of the demyelination on NCS correlated well with the clinical severity of the disease.

CONCLUSIONS

Peripheral neuropathy occurs very early in Krabbe disease and affects the nerves uniformly. Nerve conduction studies may provide a highly sensitive tool to screen this patient population.