Effect of Music on Attention and Prospective Memory in Hepatic Encephalopathy

Cirrhosis occurs when scar tissue replaces healthy liver tissue, partially blocking blood flow and preventing the liver's ability to control infections, removes bacteria and toxins from the blood, and to produce proteins to regulate blood clotting and bile to absorb fats and fat-soluble vitamins. With an estimated prevalence between five and ten percent, cirrhosis is the twelfth leading cause of death by disease, leading to 27,000 deaths per year. Heavy alcohol consumption and hepatotropic viruses (hepatitis B and C) are the major contributors to this disease's prevalence (NDDIC, 2003).

Hepatic encephalopathy (HE) is a potentially reversible, metabolically caused complication of acute or chronic liver diseases such as cirrhosis, which is characterized by neuropsychiatric abnormalities. Nearly 70% of cirrhotic patients experience mild levels of HE and approximately 30% of end-stage patients experience significant HE symptoms, many approaching coma (Mullen et al., 1999). Although the pathophysiology of HE is not yet clearly understood, the accumulation of ammonia in the brain due to the liver's inability to remove toxins (including ammonia) is thought to play a key role in the pathogenesis of HE. Other factors, which are not mutually exclusive, include increased GABA-ergic tone, selective alterations of the blood-brain barrier permeability and changes in neurotransmitter systems. The broad spectrum of symptoms in HE include forgetfulness, confusion, disorientation, concentration and memory problems, changes in mood, decreased alertness and responsiveness, changes in sleep habits, muscle tremors and stiffness, speech impairments, uncontrollable movements, agitation (Ferenci et al., 2002).

The diagnosis of HE is essentially based on clinical history and laboratory findings such as elevated ammonia levels. Additionally, specialized psychometric tests such as the number connection test (NCT), Digit Symbol Test (DST) and Psychometric Hepatic Encephalopathy Score (PHES) have been used in quantifying the minor deficits that may be present in patients with early HE.

Minimal hepatic encephalopathy (MHE) is a category of early HE without any overt neuropsychiatric symptoms but with subtle cognitive deficits (Ferenci et al., 1998). It is a common complication of cirrhosis and has been reported in 20% to 74% of patients (Dhiman et al., 2010), depending on the test used for diagnosis. It results in deficits in specific cognitive domains such as attention, vigilance, response inhibition, executive function and prospective memory. These deficits are often not apparent from a routine neurological exam or MMSE but can be detected on psychometric testing. The prompt identification and treatment of MHE are essential because MHE predicts progression to overt HE and impairs the capacity to drive which can have a significant impact on patients' quality of life (Romero-Gomez et al., 2001; Wein et al, 2004) .

Treatment of HE with or without liver transplantation has been shown to reverse the cognitive deficits and improve quality of life (Prasad et al., 2007; Sidhu et al., 2011). Although the PHES and NCT are the gold standard for diagnosing MHE, their utility is limited due to expensive copyright, a need for trained psychologists and the lack of reimbursements from insurance companies. A simpler test would therefore be beneficial to internists who could easily implement it in the clinic setting.