Introduction 

Have you ever wondered how a single metabolic disorder could silently damage the brain, causing issues with movement, balance, and muscle control? 

Cerebrotendinous Xanthomatosis (CTX), aka cerebral cholesteroinosis, is a rare but treatable inherited disease that disrupts fat metabolism, like a clogged plumbing system. This leads to a build-up of cholesterol, the cholesterol derivative cholestanol and other lipids in various tissues across different parts of the body. 

Amongst its symptoms, ataxia (the loss of coordination) and pyramidal signs (markers of motor pathways dysfunction) are the most significant motor-related neurological symptoms that are potentially progressive. 

These not only cause mobility challenges but also provide notable diagnostic clues for medical professionals. 

By exploring these two clinically observable neurological symptoms and their correlations to brain imaging, doctors can understand how CTX affects the brain and spinal pathways clearly. Hence, this paves the way for early recognition and targeted therapy to prevent or slow down the progression of mobility decline. 

What is cerebrotendinous xanthomatosis? 

Overview and onset 

Cerebrotendinous Xanthomatosis (CTX) is a rare genetic disease that affects bile acid metabolism (especially cholesterol and bile acids) in the body. With the CYP27A1 gene abnormality that prevents proper bile acid production, undigested or absorbed fats are accumulated in various body tissues, including the brain, spinal cord, tendons, lens of the eye, and even arteries, inducing a wide range of symptoms since infancy or early childhood. 

Signs and symptoms 

 One of the most common symptoms is persistent diarrhoea and liver malfunction that can seem unrelated at first. Moreover, in children or young adults, cataracts can develop early on, requiring surgery in their teens or early adulthood. 

Another symptom is Xanthomas — yellowish, painless, benign fatty lumps which may appear anywhere on the body, particularly seen around the neck, elbows, and ankles. 

Neurological symptoms include ataxia, muscle stiffness, seizures, dementia, psychiatric disturbances like hallucinations, aggression and depression. If left untreated, these behavioural changes can also become progressively more significant during a person’s twenties. 

Individual differences 

In some cases, infants with CTX (infantile-onset CTX) may present with cholestasis (reduced or absent bile flow), leading to jaundice, characterised by yellowish skin and eyes, dark urine, and pale, foul-smelling stools.

The specific symptoms and progression of CTX can vary from person to person, even twins of the same genetic deficit. 

Life expectancy 

Life expectancy without treatment is generally around 50-60 years, although some deaths are reported in infancy.¹

Understanding ataxia and pyramidal signs 

Moving the way we want depends on a highly coordinated effort between two key systems — the cerebellum and the pyramidal tracts of our brain. When affected by CTX, two distinct but occasionally overlapping patterns, ataxia and pyramidal signs, are produced. 

What is ataxia?

Ataxia describes the lack of balance and coordination. It is like drinking, affecting voluntary movements across different muscles. 

People may become unsteady when walking, swaying as if they are walking on uneven ground, falling over more than usual, or having difficulties controlling fine movements like buttoning a shirt or handwriting. They may also struggle with speech, swallowing or eye motions that require timing and precise coordination of respective oral, pharyngeal, breathing, and eye muscles. 

Most often stem from the cerebellum of the brain, which helps regulate smooth and accurate muscle movements. Movements become jerky, awkward, or clumsy even when muscle strength is kept normal.^2,3

For example, a person may reach for a cup of tea yet accidentally knock it over as their hand overshoots the target, with slurred speech and trouble swallowing.

What are pyramidal signs?

Alternatively, pyramidal signs like “stuck gear” arise from the pyramidal (corticospinal and corticobulbar) tracts, the main voluntary motor pathway that carries signals from the brain to skeletal muscles. 

While damage here manifests as spasticity (an unusual tightness or stiffness), hyperreflexia (overreactive reflexes), an involuntary, rhythmic muscle contraction (clonus), even weakness, particularly in the legs, but also arms, face, and even in the lead of slow, strained, and harsh speech.  

The Babinski (plantar) reflex, which is indicated by the big toe pointing upwards instead of downward when the sole of the foot is stimulated, has been a common clinical hallmark. 

In daily life scenarios, pyramidal signs may also make someone find their legs stiff and heavy, making it difficult to walk or move freely, alongside muscle cramps, soreness and early fatigue.^4,5

Relationships with CTX 

Thesetwo features often appear at the same time in CTX, making the clinical picture distinctive. An affected individual may experience both unsteady, clumsy movements from ataxia and stiff, spastic muscles from a pyramidal lesion. This dual burden can make walking, climbing stairs, and even simple daily activities such as rising from a chair or turning in bed progressively more difficult, leading to slowed and exhausting movements that may eventually require walking aids, a wheelchair, or manual assistance.”

Whilst many other conditions can cause ataxia and pyramidal signs alone, CTX is distinctive in that affected individuals may present with both, often in varying degrees of severity.⁶ Their coexistence, associated with other symptoms like seizures and even dementia, would strongly point clinicians towards CTX. 

Clinical and radiological correlations: connecting symptoms to imaging 

Why imaging matters

Brain imaging is a “window” into the nervous system, providing doctors with a way to see how structural changes might explain the difficulties that a person experiences in daily life. 

In CTX, magnetic resonance imaging (MRI) is particularly important in detecting characteristic structural abnormalities that mirror the patient’s symptoms. This connection — known as clinical-radiological correlation — helps translate what doctors discover into a deeper understanding of why a patient may struggle with their movement. 

Ataxia and the cerebellum

One of the hallmark motor features of CTX is ataxia, which arises when the cerebellum, the brain’s coordination centre, is affected. Cerebellar atrophy (shrinkage) and abnormal white matter changes are often seen in MRI, matching closely with the unsteady gait, not being able to walk without support or swaying, recurrent falls, and the jerky movement episodes that patients describe. That is to provide a valid, structural explanation for the patient-reported and clinically observed coordinating issues.^7,8 

Pyramidal signs and the motor pathways

Pyramidal signs in CTX tell a different yet analogously significant story. Features such as spasticity and exaggerated reflexes signify problematic pyramidal tracts — the brain’s main motor pathway that carries motor signals to muscles. On MRI, these tracts often show hyperintense signal with bright signal changes in bilateral white matter, reflecting dysfunction or damage. which correlates directly with the stiffness, weakness (spastic paraparesis) and difficulty in smooth walking seen in CTX cases, again aligning symptoms to results of imaging.^8,9

Broader brain changes in CTX

Besides the two hallmark motor features, CTX can also induce widespread white matter changes and sometimes even diffuse cerebral atrophy, involving deep brain structures like the basal ganglia. Not only can these cause ataxia and pyramidal signs, but also subtle onset, worsening Parkinsonism, and even cognitive or psychiatric changes. These can be detected through brain imaging, which can detect both motor and non-motor effects of CTX.⁹

Why clinical–radiologic correlation is important?

Essentially, the radiological pattern in CTX is distinct from other conditions. While lesions in multiple sclerosis (MS) tend to be scattered and inflammatory, those of spinocerebellar ataxias (SCAs) or degeneration are usually confined only to the cerebellum and brainstem.^10,11 However, in CTX, the combination of cerebellar atrophy and pyramidal tract hyperintensities on MRI does strongly support diagnosis when paired with clinical findings. 

Treatment and management: improving outcomes 

Despite being progressive, the good news for CTX is that it is treatable, with significantly improved outcomes under early diagnosis. 

Long-term targeted treatment 

Targeting the inability to produce chenodeoxycholic acid (CDCA) in CTX and its bile acid replacement is a cornerstone therapy in correcting the underlying metabolic defect. By restoring bile acid production, CDCA reduces toxic buildup in the body. Hence, slowing down or even reversing neurological symptoms and functional decline when implemented early.

Simultaneously, statins are used alone or together with CDCA to lower cholesterol levels, whilst the use of coenzyme Q10  can be used to improve potential myopathic weakness. 

Supportive therapies

Supportive care is crucial. Physical therapy helps manage stiffness and improve mobility, while occupational therapy can support the patient’s independence in daily activities. 

Regular monitoring

Regular monitoring with neurological exams and MRI allows neurologists to track brain damage progression and treatment response.

Summary 

Cerebrotendinous Xanthomatosis (CTX) is a rare but treatable genetic metabolic disorder, affecting fat metabolism that is harmful to both the body and the brain. In CTX, he two key neurological features — ataxia (poor coordination) and pyramidal signs (stiffness, weakness, and exaggerated reflexes)—often coexist, making movement exceptionally challenging. 

CTX can be detected through brain imaging. Brain imaging, particularly MRI, is highly valuable for its effectiveness in revealing these neurological structural changes and mirroring relevant symptoms. Early recognition is vital in starting the Chenodeoxycholic acid (CDCA) replacement therapy as soon as possible to slow down or reverse disease progression for better functioning outcomes. 

Despite the rarity of the disease, a clearer recognition of symptoms can enhance knowledge among individuals and families, whilst speeding up clinical judgement from medical professionals. It may also further encourage the development of novel therapies, genetic studies and counselling, so as to improve the overall support and improve quality of life for those affected by this rare condition.