Basic Neurosciences · Paper A
Frontal lobe function tests
Frontal/executive function is tested with a set of bedside and neuropsychological tasks, each mapped to a specific frontal sub-function. For example, imagine a patient who keeps sorting cards by the old rule even after being told it changed, that perseverationPersistently repeating a word, phrase, or action after it is no longer relevant or has already been asked for.Read more → on the Wisconsin Card Sorting Test is a classic dorsolateral prefrontal sign. In practice, this means picking the right test for the suspected sub-function, rather than treating any one task as a catch-all measure of 'frontal function'.
Verbal fluency shows reduced output with intact naming in frontal damage; category fluency counts words such as 'animals per minute', phonemic fluency counts letter-initial words such as 'FAS'. Trail Making B isolates set-shifting only when scored as B-minus-A. The Luria three-step tests motor sequencing. Go/no-go and alternating sequences test response inhibition. Proverb interpretation tests abstraction. Picture a patient whose raw Trail Making B time looks impaired, but whose Trail A was already slow for an unrelated reason. Practically, Trail Making B alone is not a pure set-shifting measure, only the B-minus-A difference isolates it from simple processing speed.
Most of the neurological exam checks whether the brain can DO things: move a limb, feel a touch, see a shape. The , especially its prefrontal (front-most) part, is different: it governs HOW a person plans, controls, and monitors their own behaviour. A patient with frontal lobe damage can move, feel, and see perfectly normally and still fail badly at everyday life, because the damage is to executive function (the set of mental skills that plan, sequence, and self-monitor behaviour), not to a single sense or muscle. That is why bedside tests of frontal function look so different from the rest of the neurological exam.
function tests are a group of simple bedside tasks used to detect executive dysfunction (problems with planning, switching, inhibiting an automatic response, and abstract reasoning) that standard strength and sensation testing will not pick up. They probe the dorsolateral (the outer, upper-front part of the frontal lobe most linked to planning and working memory) and related circuits, and are used whenever a clinician suspects a frontal lobe lesion, a frontotemporal dementia, or diffuse frontal-subcortical disease.
A common mistake is assuming a normal (MMSE, a brief global cognitive screening tool) rules out disease. It does not. The MMSE weighs heavily on memory and orientation and barely touches executive function, so a patient with a frontal lobe tumour or early behavioural-variant frontotemporal dementia can score normally on the MMSE while failing every frontal test below. Always test frontal function SEPARATELY when a frontal lesion is suspected: for example, after a change in personality or disinhibited behaviour rather than a change in memory.
Imagine asking a patient to name as many words beginning with the letter "F" as they can in one minute. This is verbal (letter) fluency, and it needs intact strategy, sustained attention, and self-monitoring to avoid repeating a word, all frontal skills, even though naming individual words itself is a function. A patient with frontal damage typically produces very few words, repeats words, or perseverates (keeps repeating the same response instead of moving to a new one), even though their vocabulary and language centres are otherwise intact. Category fluency (e.g. naming animals) is a milder version of the same test and relies relatively more on temporal lobe function, so comparing letter fluency to category fluency can help localise where the deficit sits.
The Luria three-step (fist-edge-palm) test asks the patient to copy a sequence of three hand positions (fist, edge of hand, flat palm) performed by the examiner, then repeat the sequence independently; damage causes the patient to lose the sequence, freeze, or perseverate on one position. The go/no-go task tells the patient to tap once when the examiner taps once ("go"), but not to tap at all when the examiner taps twice ("no-go"); this tests response inhibition (the ability to suppress an automatic, prepotent response), and a patient with frontal damage often taps on the no-go trial anyway. The cognitive estimates test asks a question with no memorised answer, e.g. "how tall is the average double-decker bus?", forcing the patient to reason through an estimate rather than recall a fact; frontal patients often give wildly implausible answers because they cannot apply real-world constraints to their reasoning. The Trail Making Test Part B has the patient connect alternating numbers and letters (1-A-2-B-3-C…) as fast as possible, testing cognitive flexibility and set-shifting (the ability to switch between two rule systems); a markedly slow or error-filled Part B relative to Part A (numbers only) points to frontal-executive impairment. Primitive reflexes, automatic motor responses present in infancy that are normally suppressed by a maturing frontal lobe, should not be present in a healthy adult, and their reappearance (release) signals frontal lobe or diffuse cortical disease; the grasp reflex, the palmomental reflex (a twitch of the chin muscle when the palm is stroked), and the pout/snout reflex (pursing of the lips when tapped near the mouth) are the three most commonly tested.
Executive dysfunction is not the same as a simple memory disorder or a primary language disorder. A patient with pure amnesia (memory loss) from hippocampal damage can plan and inhibit normally, and a patient with aphasia (a language disorder, typically from temporal or parietal damage) has trouble with word-finding or comprehension rather than with sequencing or inhibiting behaviour. Frontal tests are chosen specifically because they isolate planning, inhibition, and set-shifting from memory and language, which is why they are interpreted alongside, not instead of, a full cognitive assessment.
A cluster of abnormal frontal tests, especially alongside personality change, disinhibition, or apathy, raises suspicion for a lesion (tumour, stroke, or trauma) or behavioural-variant frontotemporal dementia, and should prompt structural imaging, an MRI brain scan, to look for a focal lesion or frontal-predominant atrophy. Diagnosis of frontotemporal dementia rests on defined clinical criteria, supported by imaging and, where available, formal neuropsychological testing beyond the bedside screen; the bedside tests above are a screening step, not a substitute for that fuller work-up.
There is no disease-modifying drug for frontotemporal dementia, and NICE guidance on dementia recommends a structured needs assessment, carer support, and non-pharmacological strategies for behavioural symptoms, reserving medication for specific symptom targets rather than the underlying disease. Where a discrete lesion such as a tumour is found, management follows that lesion's own pathway, surgery or oncology referral, rather than the dementia pathway. Carer education about the nature of executive dysfunction, that the patient may look physically well while genuinely unable to plan or inhibit behaviour, is itself part of good management, since it shapes realistic expectations and safety planning at home.
Questions often describe a patient who scores normally on the MMSE and use that as a distractor to make candidates rule out a frontal problem: the correct move is to recognise that the MMSE is insensitive to executive dysfunction and to ask about frontal-specific testing instead. Another trap swaps go/no-go (tests inhibition) with the Luria sequence (tests motor sequencing) in the answer options; keep each test anchored to the one specific skill it probes.
function tests (verbal fluency, the Luria sequence, go/no-go, cognitive estimates, Trail Making Part B, and primitive reflexes) probe executive function that a normal MMSE can completely miss, and an abnormal cluster should prompt imaging and NICE-guided supportive dementia care, not reassurance.