Uremic encephalopathy

Uremic encephalopathy (UE) is a brain-organic psychosyndrome caused by kidney disease with generalized or focal neurological deficits (Hoffmann 2004).

Uremic encephalopathy (UE) is one of the neurological complications of

• acute renal insufficiency
• chronic renal insufficiency (CKD) (Hoffmann 2004)

Pathogenetically, UE is suspected to cause neurotoxic damage to the peripheral and central nervous system caused by the accumulation of uremic toxins. Encephalopathy correlates with the severity of renal function impairment and is an indication for renal replacement therapy (Herold 2020). However, structural brain changes in the form of diffuse brain edema are rare (van Aken 2007).

In acute renal insufficiency the UE is more progressive and more developed than in CKD (Hoffmann 20014)

In CKD, the UE usually occurs only in the terminal stage (stage 5) (Nowack 2009)

In the early stages, rather unspecific symptoms usually occur, such as fatigue, mood swings, apathy, depression, and concentration problems (Kuhlmann 2015).

As the disease progresses, it gradually develops into

• neurological symptoms such as:
  • Reduced drive
  • Disorientation
  • Confusion
  • delirium
  • akinetic mutism in severe cases
  • asterixis (so-called "flapping tremor")
  • myoclonia
  • epileptic seizures up to the so-called nonconvulsive status epilepticus (v. Aken 2007)
  • Hyperreflexia
  • Dysarthria
  • gait disturbances
  • myoclonias
• Internal symptoms such as:
  • Fatigue
  • dyspnea
  • pale gray skin color
  • urine odor (v. Aken 2007)

EEG: In the EEG are typically found at the UE:

- a generalized slowing down of the rhythm (up to so-called theta waves)

- Occurrence of sharp-wave complexes (from steep waves)

- periodically occurring triphasic waves (v. Aken 2007)

EMG:

- Sign of denervation (v. Aken 2007)

NLG: This may give rise to comments:

- Reduction of the amplitude in the NLG (mean nerve conduction velocity) as an indication of polyneuropathy (v. Aken 2007)

MRI:

- unspecific hyperintensities in the region of the medullary canal at the T2-weighted sequence

- diffuse brain edema (occurs only rarely, however) (v. Aken 2007)

Typically there is an increase of:

• creatinine (this alone does not cause neurological symptoms)
• Urea (the urea increase is primarily responsible for the neurological symptoms) (v. Aken 2007)

• chronic dialysis encephalopathy (this occurred frequently until the 1990s, nowadays it is only rare - due to the use of aluminum-free dialysate preparation; it is caused by intoxication with aluminum and progresses like a rapidly progressive dementia; therapy: deferoxamine therapy [Kuhlmann 2015])
• other forms of hypoxic-toxic encephalopathy
• subdural hematoma (occurs frequently in dialysis patients; diagnosis by imaging)
• dysequilibrium syndrome (neurological symptoms are caused by a forced normalization of retention values or electrolytes) (v. Aken 2007)
• hypertensive encephalopathy
• systemic vasculitis
• electrolyte imbalances
• sepsis (Kuhlmann 2015)

The treatment of a UE consists in normalizing the retention values (especially of the urea). (v. Aken 2007)

Normalisation of the metabolic derailment usually results in rapid and complete remission of the neurological symptoms (Hoffmann 2004).

1. van Aken H et al (2007) Intensive Care Medicine. Georg Thieme Publisher 1160
2. Herold G et al (2020) Internal medicine. Herold Publishing House 642
3. Hoffman G F et al (2004) Metabolic diseases in neurology. Georg Thieme Publisher 200
4. Kuhlmann U et al (2015) Nephrology: Pathophysiology - Clinic - Kidney replacement procedure. Thieme Publishing House 435 - 436
5. Nowack R et al (2009) Dialysis and Nephrology for Specialists. Springer publishing house 177