Small fibre function in patients with meralgia paresthetica.
BACKGROUND
Patients with meralgia paresthetica (MP) usually experience not only paraesthesias and decreased tactile sensation, but also painful dysesthesias in the distribution of the lateral femoral cutaneous nerve (LFCN). We aimed at assessing whether there is any functional impairment of small fibres of the LFCN in patients with MP.


METHODS
We carried out a clinical, psychophysical and neurophysiological study in 14 patients with MP and 14 healthy control subjects. We assessed pain in the last 2months, thermal thresholds and small fibres conduction by using a visual analogue scale (VAS-pain), quantitative sensory testing (QST) and contact heat-evoked potentials (CHEPs), respectively. Data were grouped for control subjects, non-affected side and affected side of patients with MP.


RESULTS
Patients marked a VAS-pain of 4.3+/-1.5. In the affected side, thresholds for warm and heat pain sensations were elevated and the amplitude of CHEPs was reduced in comparison to the non-affected side and controls (Bonferroni's test; p<0.001 for all comparisons). The amplitude of CHEPs correlated inversely with duration of the symptoms (r=-0.57, p=0.002), as well as with heat pain thresholds (r=-0.18, p=0.01). No significant correlations were found between CHEPs and VAS-pain (p>0.05 for all correlations).


CONCLUSIONS
Besides the involvement of large myelinated fibres, partial loss of function in small fibres may also account for the painful symptoms of patients with MP, especially in those with longer disease duration.
Medical Sciences Post-Graduation Course, UFRGS School of Medicine, Porto Alegre, Brazil EMG Unit, Department of Neurology, Hospital Clínic, Universitat de Barcelona, Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), Barcelona, Spain Department of Neurophysiology, Hospital Universitari Vall d'Hebron, Barcelona, Spain.
Pedro
P
Schestatsky
Estela
E
Lladó-Carbó
Jordi
J
Casanova-Molla
Silvio
S
Álvarez-Blanco
Josep
J
Valls-Solé
D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology*; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D017288:Pain Threshold; D010292:Paresthesia / Q000503:physiopathology*; D012867:Skin / Q000294:innervation* / Q000503:physiopathology*