Other dementia

• Asymmetric, progressive stiffness and clumsiness, often starting in one limb, sometimes described as the limb feeling ‘foreign’ or acting on its own (alien limb phenomenon)
• Difficulty with planning movements (apraxia), language difficulties and changes in thinking or behaviour can also occur, usually alongside the asymmetric motor signs.

Several different pathologies can cause corticobasal syndrome, eg an abnormal build-up of tau protein (ie a pathological disease called corticobasal degeneration) or amyloid and tau (ie Alzheimer’s disease pathology), causing shrinkage in specific brain regions controlling movement and higher thinking skills, often affecting one side of the brain more than the other.

• Involuntary, jerky, dance-like movements (chorea) affecting the face, limbs or trunk are often the most visible feature
• Progressive difficulty with planning, concentration and processing speed
• Mood changes (irritability, depression or apathy)
• In some cases, personality change.

Symptoms typically emerge in mid-adulthood, and there is a family history in most cases, given its inherited nature.

An inherited genetic mutation (HTT gene) leading to production of an abnormal huntingtin protein, which is toxic to nerve cells, particularly in deep brain regions controlling movement.

• Prominent difficulty forming new memories, often with relative preservation of long-established memories and general knowledge
• Some people confabulate, confidently describing events that did not happen, without intending to deceive.

History of long-term heavy alcohol use and poor nutrition is typical.

Other thinking skills can be relatively preserved, particularly if identified and treated early.

Thiamine (vitamin B1) deficiency, often due to alcohol use, causing damage to brain regions involved in memory formation.

• Gradually worsening walking difficulty (small, shuffling steps or difficulty initiating walking)
• Thinking changes (slowed thinking, reduced attention)
• Urinary incontinence.

Walking difficulty often appears first and is usually the most treatment-responsive feature.

Symptoms can sometimes improve following surgical treatment.

The fluid-filled spaces in the brain (called ventricles) are enlarged.

Surgical treatment, when performed, is often aimed at shunting the cerebrospinal fluid out of the brain.

Normal pressure hydrocephalus is often related to underlying neurodegenerative disease processes like Alzheimer’s disease (amyloid and tau build-up) or tau protein build-up.

• Rapid decline in thinking and memory over weeks to months (much faster than other dementias)
• Often accompanied by involuntary muscle jerks (myoclonus), unsteady movement and behavioural change.

Because CJD progresses so rapidly, it is usually recognised and investigated urgently. It is extremely rare.

CJD is caused by an abnormal, misfolded protein called a prion.

Unlike other proteins involved in dementia, this misfolded prion protein can cause normal proteins nearby to also fold abnormally, leading to a chain reaction that spreads rapidly through the brain and causes widespread damage.