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The NECSA Classification 

NECSA mnemonic diagram.png

Psychobehavioural symptoms presenting in the setting of neurological disorders can be exceptionally challenging diagnostically.  The clinician is often faced with a multitude of potential contributory factors and may only have very limited time in which to comprehensively consider their interplay.  It can be tempting to save time by using heuristic mental shortcuts based on clinical intuition.  However, this risks the misattribution of neuropsychiatric symptoms to ‘red herring’ mechanisms that happen to stand out in the history, at the expense of a broader systematic consideration of potential differentials.  The NECSA Classification* was developed for the busy clinician as a checklist of pathogenetic mechanisms which is conceptually clear, easy to recall and time-efficient to apply.

  • Hassan I (2015). The Neuropsychiatric Effects of CNS Structural Abnormalities (NECSA) classification: An aid to differential diagnosis. Australian and New Zealand Journal of Psychiatry 49: 943.


The acronym ‘NECSA’ stands for Neuropsychiatric Effects of CNS Structural Abnormalities and also serves as a mnemonic for five classes of pathogenetic mechanisms:


  1. Network disruption. A structural abnormality, such as encephalomalacia, gliosis or a tumor, causes disruption in a functional network resulting in neuropsychiatric symptoms.

  2. Electrical effects. The structural abnormality triggers focal seizures which lead to neuropsychiatric symptoms. 

  3. Chemical effects.  Psychobehavioural symptoms arise due to neuroendocrine effects, such as from excess hormone production by a secretory tumor (for example of the pituitary or hypothalamus) or from hormone deficiency due to damage in these structures. 

  4. Side effects of treatment. Neuropsychiatric symptoms can arise iatrogenically from various types of treatment for a lesion, e.g. medication, surgery, or radiotherapy.

  5. Alternative effects. The patient’s neuropsychiatric symptoms may be related to factors independent of the structural abnormality.  These may include the interplay between recent psychosocial stressors and remote psychodevelopmental influences, as well as other factors, e.g. genetic, neurodevelopmental and neurodegenerative factors.

The above items are used as a checklist for pathogenetic mechanisms in the Neuropsychiatric Formulation Chart*. Alternatively, for neuropsychiatric presentations in the absence of demonstrable structural change in the brain, the clinician may wish to use a general checklist for pathogenetic mechanisms (such as the VITAMINS surgical sieve). The Neuropsychiatric Formulation Chart comes in two versions to accommodate both options.  


  • Hassan I (2019). Formulation in neuropsychiatry: a stepwise approach. Australasian Psychiatry 27: 411-2.   

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