title: A pain model with a neuropathic somatosensory lesion: Morton neuroma.
abstract: A randomized, double-blind, three-period cross-over study was performed to characterize the sensory phenotype and pain demographics in patients with Morton neuroma (n=27) and to explore the effects of local administration (2mL) of placebo and lidocaine (1 and 10mg/mL) around the neuroma. Using the pain quality assessment scale (PQAS), the highest rating was seen for unpleasant pain and intensity of deep pain and the lowest for sensitive skin. Ongoing pain was reported in 32% of patients. Patients reported mild to moderate average pain, and that pain had interfered with sleep only marginally. Quantitative sensory testing (QST) measurements in the innervation territory showed hypophenomena or hyperphenomena in all patients, indicating that all had neuropathy. There was no particular QST modality that appeared to be specifically affected. Even the high-dose lidocaine resulted in limited effects on nerve-impulse conduction as judged by the effect on QST variables. However, both doses of lidocaine significantly reduced pain after step-ups, compared to placebo, indicating that lidocaine in this setting affected predominantly impulse generation and not impulse conduction. Following placebo treatment, pain after step-ups was similar in patients with and without hyperalgesia, indicating that the presence of hyperalgesia does not affect the pain intensity evoked by step-ups or walking. This pain model in patients with Morton neuroma allows investigation of drugs in a cross-over design and provides an opportunity to explore drug effects on both pain and QST variables. Commonly, neuromas are surgically removed and can be characterized in depth in vitro, thereby allowing close links to be established between pathophysiology and drug effect.
authors.affiliation: AstraZeneca R&D, Södertälje, Sweden Sport Med, Stockholm, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Quiding
authors.forename: Christian
authors.initials: C
authors.lastname: Åkermark
authors.forename: Märta
authors.initials: M
authors.lastname: Segerdahl
authors.forename: Ingalill
authors.initials: I
authors.lastname: Reinholdsson
authors.forename: Hanna
authors.initials: H
authors.lastname: Svensson
authors.forename: Bror
authors.initials: B
authors.lastname: Jonzon
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000779:Anesthetics, Local / Q000009:adverse effects / Q000627:therapeutic use; D003080:Cold Temperature; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D005528:Foot / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D006930:Hyperalgesia / Q000209:etiology / Q000523:psychology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008012:Lidocaine / Q000009:adverse effects / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009437:Neuralgia / Q000188:drug therapy / Q000209:etiology* / Q000503:physiopathology; D009463:Neuroma / Q000150:complications* / Q000188:drug therapy / Q000503:physiopathology; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D010812:Physical Stimulation; D018401:Sample Size; D013697:Thermosensing / Q000502:physiology; D055815:Young Adult
chemical_list: D000779:Anesthetics, Local; D007473:Ion Channels; D008012:Lidocaine
keywords: Demographics; Lidocaine; Morton neuroma; Pain model; Phenotype; Quantitative sensory testing