Long Latency Reflexes in Clinical Neurology: A Systematic Review

Abstract

Background: Long latency reflexes (LLRs) are impaired in a wide array of clinical conditions. We aimed to illustrate the clinical applications and recent advances of LLR in various neurological disorders from a systematic review of published literature. Methods: We reviewed the literature using appropriately chosen MeSH terms on the database platforms of MEDLINE, Web of Sciences, and Google Scholar for all the articles from 1st January 1975 to 2nd February 2021 using the search terms “long loop reflex”, “long latency reflex” and “C-reflex”. The included articles were analyzed and reported using synthesis without meta-analysis (SWiM) guidelines. Results: Based on our selection criteria, 40 articles were selected for the systematic review. The various diseases included parkinsonian syndromes (11 studies, 217 patients), Huntington’s disease (10 studies, 209 patients), myoclonus of varied etiologies (13 studies, 127 patients) including progressive myoclonic epilepsy (5 studies, 63 patients) and multiple sclerosis (6 studies, 200 patients). Patients with parkinsonian syndromes showed large amplitude LLR II response. Enlarged LLR II was also found in myoclonus of various etiologies. LLR II response was delayed or absent in Huntington’s disease. Delayed LLR II response was present in multiple sclerosis. Among the other diseases, LLR response varied according to the location of cerebellar lesions while the results were equivocal in patients with essential tremor. Conclusions: Abnormal LLR is observed in many neurological disorders. However, larger systematic studies are required in many neurological disorders in order to establish its role in diagnosis and management.

Utility of Neurophysiological Evaluation in Movement Disorders Clinical Practice

“…The techniques used included polymyography in all cases, and in some cases EEG recording with SEP (n = 25, 19%), backaveraging (n = 17, 13%), or peripheral stimulation with assessment of long-latency reflex [13][14][15] (n = 25, 19%) were used to localize the origin of myoclonus. 12,16 Tremor In 21% (n = 106) of the cases, tremor evaluation was the reason for referral (Table 2).…”

Long latency reflexes of the median nerves in healthy adults

“…Therefore, the main clinical use of LLR has been in the assessment of upper motor neuron disorders. LLR have been studied mainly in Parkinson disease, spasticity, dystonia, multiple sclerosis, motor neuron disease, and spinocerebellar ataxia 6–14 . There have been very few assessments of their utility in peripheral neuromuscular disorders, although the technique may add value in situations in which standard nerve conduction studies are incompletely diagnostic (eg, early or acute neuropathy, such as Guillain‐Barré syndrome) 15,16 .…”

“…LLR have been studied mainly in Parkinson disease, spasticity, dystonia, multiple sclerosis, motor neuron disease, and spinocerebellar ataxia. [6][7][8][9][10][11][12][13][14] There have been very few assessments of their utility in peripheral neuromuscular disorders, although the technique may add value in situations in which standard nerve conduction studies are incompletely diagnostic (eg, early or acute neuropathy, such as Guillain-Barré syndrome). 15,16 Most reference values have been derived from old studies of small cohorts of participants, or individual laboratory data.…”