Human cremaster muscle and cremasteric reflex: A comprehensive review

Area of Science:

• Neuroscience
• Anatomy
• Physiology

Background:

• Human research on the cremaster muscle (CM), cremasteric reflex (CMR), and genitofemoral nerve (GFN) is scarce.
• Clinical applications of these structures often lack detailed electrophysiological and histological data.

Purpose of the Study:

• To provide a comprehensive review of the human CM and CMR.
• To synthesize findings from previous publications and relevant literature.

Main Methods:

• Electromyography (EMG) of the CM using needle electrodes.
• Tactile and electrical stimulation for CMR, with transcranial magnetic stimulation (TMS) and lumbar root stimulation.
• GFN stimulation via surface electrode at the anterior superior iliac spine.

Main Results:

• CM striated fibers exhibit multiple motor end plates.
• CM EMG findings in chronic neurogenic disorders resemble limb muscles.
• TMS elicited clear motor responses from CM.
• Absent or delayed GFN motor conduction to CM observed in inguinal hernia patients.
• Abnormal CM EMG detected in 40% of patients with premature ejaculation.

Conclusions:

• The CM possesses unique morphological and physiological characteristics compared to other skeletal muscles.
• Intersegmental sacrolumbar reflexes are valuable for assessing ejaculatory dysfunction.