The Gastroparesis Cardinal Symptom Index (GCSI), a subset of the Patient Assessment of Gastrointestinal Disorders Symptom Severity Index (PAGI-SYM), is a questionnaire that is commonly used to establish symptom severity in patients with gastroparesis. It is comprised of 3 subscales—nausea and vomiting, postprandial fullness and early satiety, and bloating—which are averaged to provide a total GCSI score. Symptoms over the 2 weeks prior to administration of the questionnaire are assessed and rated from 0 (none) to 5 (very severe).22 Grading the severity of gastroparesis may take into account symptoms, quality of life, and gastric emptying. One commonly used grading system assigns a grade from 1 to 3, with grade 1 being mild gastroparesis, grade 2 being compensated gastroparesis, and grade 3 being gastric failure with refractory symptoms that are uncontrolled.18,23 Quality-of-life surveys also suggest that gastroparesis independent of other factors leads to a worse quality of life.24
Indications for GES
Gastric electric stimulator implantation is a surgical procedure with inherent risks and complications and is reserved for patients with intractable symptoms of gastroparesis who remain symptomatic despite treatment attempts with dietary management, antiemetic agents (eg, compazine, phenergan, and ondansetron), and prokinetic agents (eg, metoclopramide, erythromycin, and domperidone). Symptom modulators such as nortriptyline and mirtazapine are occasionally tried.
Surgical intervention can be considered upon failure of medical treatment measures. At least a year of documented care provided by a physician specializing in gastroparesis is suggested for surgical consideration. The gastric electric neurostimulator is approved by the FDA as a HUD for the care of patients with idiopathic and diabetic gastroparesis, performed on a compassionate basis. GES implantation requires Institutional Review Board approval at the institution, and patients are required to have documented delayed gastric emptying.
It is important to remember that the GES device is incompatible with magnetic resonance imaging (MRI) and explantation of the device is necessary prior to MRI. As such, in patients with anticipated need of frequent MRI, such as those with multiple sclerosis, serious consideration should be given to alternative strategies prior to focusing on this modality.
Device Placement
GES was devised to improve gastric emptying. The Enterra GES system uses high-frequency, low-energy electric stimulation. An alternative method is true gastric pacing that uses high-energy, low-frequency stimulation to entrain the gastric slow waves and subsequent contractions at 3 cycles per minute (cpm). Gastric pacing has greater energy requirements than GES, which makes the size of the stimulator too large to be practical. In pilot animal studies, GES produced an accelerating effect on gastric emptying, but in human studies GES had an inconsistent effect on gastric emptying. Studies have suggested that GES influences the proximal stomach, with a reduction of gastric tone,25 and also that GES has an afferent modulatory mechanism.26
