Question 20

College Answer

Definition:

Change in behaviour and or mental processes from baseline associated with continuous epileptiform EEG changes but without major motor signs. NCSE comprises a group of syndromes with a wide range of response to anti-convulsants from virtually self-limiting forms to refractory forms. No universally accepted definition yet exists

Difficulties in Diagnosis:

Little agreement on diagnostic criteria, clinical forms, consequences and treatment Difficulty telling when coma is due to ictal symptomatology and differentiating it from non ictal symptoms associated with underlying pathology such as posthypoxic, metabolic or septic encephalopathies and effects of sedative drugs.

On EEG there are cross over features between epilepsy and encephalopathies which are being still standardized and the diagnosis of NCSE should not be on EEG changes alone.

Early recognition and treatment are essential to optimize response to treatment and to prevent neurological and systemic sequelae. However overdiagnosis and aggressive use of anticonvulsants may also contribute to morbidity and mortality.

Risk factors:

• Systemic infection in patient with pre-existing epilepsy
• Stroke including intracerebral & subarachnoid haemorrhages
• Dementia 
• Neoplasia
• Previous neurosurgery
• Patients with pre-existing epilepsy have a lower mortality (3%) than where NCSE is due to acute medical disorders (27%).

Management: 

• Difficulties in diagnosis as outlined above
• Index of suspicion in patients with risk factors and suggestive clinical features

Investigations

• Blood tests to exclude electrolyte abnormalities (low Ca, low Mg), liver and renal dysfunction, haematological causes (e.g TTP) 
• Lumbar puncture: looking for CNS infection
• EEG and response on EEG and clinically to Benzodiazepines
• MRI to exclude structural cause not evident on CT

Treatment

• Treatment of underlying cause Benzodiazepines: Diazepam or Lorazepam
• Valproate: if failure to respond to benzodiazepines
• Keppra increasingly used
• Reversal of factors that lower seizure threshold eg drugs such as cefepime, fever, hypoxia, hypoglycaemia, hyponatraemia

Discussion

Non-convulsive status epilepticus comes up often enough to merit its own little summary page.

a)

The diagnosis of non-convulsive status epilepticus requires the following:

• A change in behaviour or responsiveness
• A duration of change for longer than 30 minutes
• No obvious seizure activity
• Epileptiform discharges on EEG

b)

The difficulty in making the diagnosis is the protean nature of its manifestations, which range from confusion and delirium to unconsciousness. As there are numerous pathologies which are more common and which can present in this way, the diagnosis (by EEG confirmation) is frequently delayed.

c)

Risk factors for non-convulsive status epilepticus are similar to the risk factors for epilepsy in general, and include:

• Structural brain disease:
  • Stroke
  • Space occupying lesion (blood, pus or tumour)
  • Gliosis due to previous stroke, brain injury or neurosurgery
  • Dementia
• Metabolic
  • Sepsis in a patient with known epilepsy

d) Approach to management:

• Attention to the ABCS, with management of life-threatening problems simultanous with a rapid focused examination and a brief history
• Supportive management
  • Assessment of the airway, and airway control if appropriate
  • Ventilation support, or supplemental O₂ in the spontaneously breathing patient
  • Circulatory support to ensure normotension
  • Endocrine and metabolic support to ensure correction of electrolyte derangement and control of blood glucose
• Specific management
  • Benzodiazepines: midazolam or lorazepam
  • Anticonvulsants: phenytoin, valproate or levitiracetam

Oh's Intensive Care manual:

Chapter 49   (pp. 549) Disorders  of  consciousness  by Balasubramanian  Venkatesh

Chapter   50   (pp. 560) Status  epilepticus  by Helen  I  Opdam

Fountain, Nathan B. "Status epilepticus: risk factors and complications."Epilepsia 41.s2 (2000): S23-S30.

Meierkord, Hartmut, and Martin Holtkamp. "Non-convulsive status epilepticus in adults: clinical forms and treatment." The Lancet Neurology 6.4 (2007): 329-339.