Vascular

Mrs Howells does have risk factors for vascular pathology - HTN, T2DM,  little exercise and age.

However:

TIA - The history doesn't fit the classical presentation, however the fall could have been due a sudden bout of dizziness from a TIA and the subsequent headaches, confusion and drowsiness  can be associated. However, an episode of light-headedness can lead to a trip and fall - leading to an intracranial bleed - can equally explain the situation.

Stroke - Again as above, none of the classical symptoms are present (and there is a normal neuro/ crainal nerves exam). Furthermore her ABCD2 score is 2, in reference to the TIA above, making her risk of a stroke low and her risk of a later stroke also is low. Don't forget also that strokes come in two flavours - ischaemic and haemorrhagic.

Vascular dementia - Here the history doesn't quite match - classically this is a dementia with a deterioration in a stepwise manner, associated with vascular events. Although, it could explain the recent diagnosis of mild cognitive impairment - and therefore this event is the step progression.

Common things are common and a HI enough to cause a laceration in an older patient should make you worry about a intracranial bleed, which in itself can cause confusion and drowsiness. That being said, there is a small chance of a non-classical presentation and a CT head will help differentiating

Infective/ Inflammatory

UTI - In older patients, UTIs are one of the most common culprits for acute confusion/ delirium. With lower urinary tract symptoms (LUTS - dysuria, freqency) this likelihood is increased. Unfortunately, the older population also suffer from more urological problems and this can be unrelated to an ongoing UTI. Foul smelling urine, which may or may not be evident from the bedside, and a urine dip positive for nitrates also point towards a UTI diagnosis.

Sepsis/Systemic inflammatory reponse syndrome (SIRS) - While this is an urgent clinical concern, the history nor examination support this diagnosis (save the confusion).

Other infections - Chest infections (Lower respiratory tract infections -LRTI) fall into this category, and with the CURB65 score including confusion as one of the points, it is valid to check for it. However, the lack of a history and a cough reduces the likelihood. Regardless, a quick chest examination may be beneficial if a cause of confusion is not clear (+/- a Chest XR if indicated).

There is a lack of history to suggest other infections. Blood works looking for raised inflammatory markers is your next best investigation.

Traumatic

Head injury (HI) - An accidental fall and HI can result in an intracranial bleed. Given the injury is also sufficient to cause a laceration and the patient is deteriorating (reduced GCS), a bleed should be investigated regardless of any other causes of confusion. As a CT Head is the gold standard, it will conveniently also help identify an obvious stroke/ infarct.

Autoimmune

Thyroid disease - hypothyroid is a relatively common cause of confusion, and Mrs Howells is known to be hypothyroid but treated with levothyroxine. It is not too much of a stretch to suggest that with her cognitive impairment that she may forget to take her medication and therefore become clinically hypothyroid.

However, in the absence of more symptoms this is less likely.

It is not unreasonable to request a one off thyroid function test as part of your confusion screen.

Metabolic

Electrolyte disturbances - these can be insidious and can be caused by dehydration and medications. The history doesn't fit well as the daughter claims her mother was her usual self but became confused after the fall. This rapid onset would point away from a disturbance, but again a blood test as part of your screen is helpful. Na+, K+ (found in U&Es)and Ca2+ (often in bone profiles) are the key electrolytes.

Hypoglycaemia - T2DM controlled by metformin and diet is unlikely to cause hypoglycaemia as a whole. The history does fit in parts with this diagnosis - from the light-headedness , collapse, confusion and reduced GCS. A formal blood glucose or a bedside fingerprick BM should help rule this out.

Iatrogenic/ idiopathic

Medication - as mentioned under metabolic, medications, changes in medications or errors in taking medication can lead to electrolyte imbalances as relatively common side effects or as the key mechanism of action. Equally you may have to consider medication causing postural hypotension manifesting as light-headedness, leading to a fall. A careful history may help with this alongside bloods.

Culprits:

Antihypertensives - Amlodipine, Doxazocin

Diuretics - Bendroflumethiazide

Neoplastic

Brain tumour - the acute and sudden onset history, lack of relevant symptoms and normal examinations makes this unlikely.  This should not be high in your differential but kept in the back of your mind. The CT head will help with this as a bonus.

Degenerative

Cognitive impairment - It can be easy to assume that a confused patient with dementia is confused because of the dementia progressing vs another process, this should therefore be a diagnosis made by exclusion of the other more pressing matters. Additionally the history doesn't fit, save for the potential of a vascular dementia worsening.