Ammonia: what adult neurologists need to know

Abstract

Hyperammonaemia is often encountered in acute neurology and can be the cause of acute or chronic neurological symptoms. Patients with hyperammonaemia may present with seizures or encephalopathy, or may be entirely asymptomatic. The underlying causes are diverse but often straightforward to diagnose, although sometimes require specialist investigations. Haemodialysis or haemo(dia)filtration is the first-line treatment for acute severe hyperammonaemia (of any cause) in an adult. Here we discuss our approach to adult patients with hyperammonaemia identified by a neurologist.

Risk factors and outcome of hyperammonaemia in people with epilepsy

“…VPA also increases renal ammonia production by enhancing glutamine uptake in the renal mitochondria. Glutamine is subsequently converted to glutamate and ammonia in the renal tubules [31]. Apart from the well-known association of HA with VPA therapy, our data showed a potential association of HA with other ASMs, such as STP and OXC.…”

“…VPA also increases renal ammonia production by enhancing glutamine uptake in the renal mitochondria. Glutamine is subsequently converted to glutamate and ammonia in the renal tubules [ 31 ].…”

“…Reduction or discontinuation of VPA along with dietary protein intake monitoring are suggested as initial therapeutic approaches. Carnitine supplementation if carnitine deficiency is detected, and addition of nitrogen scavenger medications, have been recommended as additional considerations within the therapeutic strategy [ 31 ].…”

Late-onset ornithine transcarbamylase deficiency mimicking a focal opercular syndrome

“…Early diagnosis is critical for effective treatment and to prevent long-term complications of hyperammonaemia 18. Testing plasma ammonia should be considered in patients with transient episodes of altered consciousness or seizures, even when there is no evidence of renal or hepatic dysfunction 19. Late-onset OTC deficiency may mimic autoimmune encephalitis and patients may have more focal symptoms, such as an atypical opercular syndrome in this case.…”