Basic Neurosciences · Paper A
Prefrontal syndromes
Damage location inside the prefrontal cortexThe front part of the brain responsible for planning, judgement and controlling impulses.Read more → matters because different parts control planning, impulse control, and motivation: the prefrontal cortex is not one uniform region, and damage to each part produces a distinct behavioural picture. For example, imagine three patients with damage to three different prefrontal areas: one cannot plan a simple task, one behaves rudely and impulsively in public, and one sits silently and initiates nothing. In practice, matching that behaviour to the damaged region is exactly what the exam and the clinic both test.
Dorsolateral damage gives a dysexecutive picture, impaired planning, set-shifting (switching between rules) and working memory. Orbitofrontal damage gives disinhibition, impulsivity, explosive outbursts, socially inappropriate behaviour, with planning relatively preserved. Medial (anterior cingulate) damage gives apathy, reduced spontaneous behaviour and speech, and reduced emotional reactivity, which in its most severe form becomes akinetic mutismA complete absence of speech despite the physical ability to speak.Read more → (a state of wakeful silence and stillness). Picture a patient who initiates no conversation and sits motionless for hours despite being awake and alert: that pattern points to medial, not orbitofrontal, damage. In practice, testing planning, social behaviour, and spontaneous initiation separately matters, since each maps to a different region. Kleine-Levin syndrome, a rare periodic hypersomnia disorder, is a distinct mimic worth flagging here. During an episode, functional imaging shows reduced prefrontal (and thalamic) activity. That is a transient, reversible functional change, not the persistent structural damage of a true frontal lobeThe front part of the brain, involved in planning, personality and impulse control.Read more → syndrome, and it normalises between episodes.
A fresh doctor might lump all damage into one generic "personality change" bucket. That loses the exam-relevant and bedside-relevant distinction: the has at least three functionally separate zones, and each produces its own recognisable behavioural syndrome. Hold the phrase THREE ZONES, THREE PICTURES through every section below.
The sits at the front of the frontal lobe and governs planning, impulse control, social behaviour, and motivation. Damage here does not usually cause the paralysis or sensory loss (loss of normal feeling) seen with damage to other brain regions; instead it produces a behavioural or personality change, and WHICH change depends on which of the three main zones (dorsolateral, orbitofrontal, or medial (anterior cingulate)) is affected.
A common mistake is assuming any patient with cognitive complaints and damage has memory loss like Alzheimer's disease. Frontal lobe syndromes characteristically spare basic perception and memory on formal testing: a patient can score normally on a standard memory test yet still be unable to plan a simple task, hold down a job, or behave appropriately in public, because the deficit is executive and behavioural, not mnemonic (memory-related).
Three patients with damage to three different prefrontal zones can look completely different: one cannot plan a simple multi-step task, one behaves rudely and impulsively in public, and one sits silently and initiates nothing despite being awake and alert. Matching that behavioural pattern to the damaged zone, rather than diagnosing a vague " syndrome," is exactly what both the exam and the bedside assessment test.
Dorsolateral prefrontal damage produces a dysexecutive syndrome (a pattern of impaired higher-level planning and organisation): poor planning, impaired set-shifting (difficulty switching between rules or strategies), and reduced working memory (the ability to hold and manipulate information briefly). For example, a patient who fails at organising a simple errand involving several steps, despite normal memory on formal testing, such as someone who cannot plan a shopping trip within a budget, is showing this pattern.
Orbitofrontal damage produces disinhibition, impulsivity, explosive outbursts, and socially inappropriate behaviour, with planning ability relatively preserved: this is the pattern classically associated with personality change after head injury. Medial (anterior cingulate) damage instead produces apathy, reduced spontaneous speech and behaviour, and blunted emotional reactivity; in its most severe form this becomes akinetic , a state of wakeful silence and stillness in which the patient is awake but initiates nothing.
Dorsolateral prefrontal syndrome, with its dysexecutive planning deficit, should not be confused with orbitofrontal syndrome's disinhibition, since the former spares social behaviour while the latter spares planning. Medial frontal (anterior cingulate) syndrome's apathy and akinesia (loss of spontaneous movement or initiative) is the near-opposite clinical picture to orbitofrontal disinhibition, even though both arise from prefrontal damage. syndromes as a group should not be confused with the amnesia (significant memory impairment) of medial damage, since frontal damage spares memory while temporal lobe damage characteristically does not. Apathy from medial frontal damage should also be distinguished from depression, since a depressed patient typically reports low mood and is often distressed by their reduced activity, whereas a patient with medial frontal apathy is usually unconcerned by it.
Diagnosis relies on a careful history from family or carers describing the behavioural change, since the patient themselves, especially with orbitofrontal or medial damage, often lacks into what has altered. Structured cognitive and executive-function assessment (tests of planning, set-shifting, and working memory, such as the Trail Making Test or verbal fluency tasks) helps confirm a dysexecutive pattern while formal memory testing stays normal, which is itself diagnostically useful. Imaging (CT or MRI) is then used to identify the underlying cause (trauma, tumour, or neurodegeneration such as frontotemporal dementia) since the behavioural pattern alone tells you WHICH zone is affected but not WHY.
Management is largely supportive: structured routines and environmental adaptation for dysexecutive patients, behavioural strategies and, where needed, medication for impulsivity or agitation in orbitofrontal presentations, and treating any reversible underlying cause first-line, following standard neuropsychiatric assessment pathways aligned with NICE guidance on assessing cognitive and behavioural change. Family and carer education is a first-line, practical intervention in its own right, since much of the burden of these syndromes falls on relatives managing day-to-day disinhibition or apathy at home.
The high-yield pearl: normal memory testing plus a clear behavioural change points to frontal, not temporal, lobe pathology. Vignettes often describe a patient with normal memory testing but obvious behavioural change and expect the candidate to recognise a frontal, not temporal, lobe problem. Another trap presents akinetic and expects localisation to the medial frontal or anterior cingulate region rather than mistaking it for depression or . A further trap gives a post-head-injury personality change with impulsivity and expects recognition of orbitofrontal, not dorsolateral, damage.
Match the behavioural picture to the prefrontal zone: dorsolateral damage causes a dysexecutive syndrome with poor planning and set-shifting, orbitofrontal damage causes disinhibition and impulsivity, and medial (anterior cingulate) damage causes apathy that can progress to akinetic . All three spare basic memory and perception, which is the key discriminator from medial amnesia, and diagnosis rests on collateral history, executive testing, and imaging to find the underlying cause, with management centred on supportive structure, behavioural strategies, and treating that cause.