Dementia In Corticobasal Degeneration

What is Corticobasal Degeneration (CBD)?

It presents as a heterogenic group with the clinical and pathological heterogenicity seen in CBD.

Core Features of CBD

• Progressive asymmetric rigidity
• Apraxia is also seen.
• There is cortical and basal ganglia dysfunction.

History

First identified in 1967, 3 patients had progressive asymmetric rigidity and apraxia. In the 1990s, it was named CBD.

Epidemiology

The age of onset is 45 to 77 years.

Etiology

The patients having CBD usually are sporadic cases. It is seen that there is an H1 haplotype of the MAPT gene that is associated with CBD.

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Diagnosis and Clinical Features

Core features: Progressive asymmetric rigidity, Apraxia

Additional symptoms: Alien limb phenomenon, cortical sensory loss, myoclonus, mirror movements, dystonic posturing, and tremors.

These are minimal at rest and increase with action. One should know this because tremors often occur in CBD, but it also occurs in Parkinson's disease as well. So, you should know how to differentiate it clinically. Along with this, patients may also have cognitive impairments such as attention, executive functioning, language, memory, and visuospatial function. Learning all these cognitive impairments may occur, and patients may also have aphasia.

Other symptoms may also be seen, such as frontal behavioral symptoms and speech impairment, and they may occur in the early course or at the onset. Ocular motor apraxia may also be seen; the patient has difficulty initiating saccades and difficulty in voluntary gaze.

Laboratory Examination

MRI: Asymmetrical cortical atrophy (esp. In front parietal regions). It is more prominent in the contralateral hemisphere to the side of the symptom. If the symptoms are more towards the right side, then the atrophy will be seen on the left side.

May have asymmetric atrophy in basal ganglia and cerebral peduncles. As the name suggests, there is corticobasal degeneration in the cortex and basal ganglia.

SPECT, PET:  Asymmetrical hypoperfusion in the parietal, frontal cortex, and basal ganglia.

Pathological Finding

There is focal cortical neuronal loss in the frontal, parietal, and temporal lobes. Neuronal loss in substantia nigra. The hallmark is balloon neurons. This is not required for making a diagnosis, as many times you see these hallmark findings in pathology. Gallyas and astrocytic plaques and threads Tau-positive oligodendroglial coiled bodies may also be seen in patients with CBD.

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Differential Diagnosis

PSP (progressive supranuclear palsy) can be an important differential diagnosis as there is a significant overlap in pathology and symptoms.

Parkinson's Disease

Tremors in CBD are minimal at rest and increase with action. CBD patients are not responsive to Parkinsonian drugs. Parkinson's drugs that we use in Parkinson's disease are less effective in CBD.

Dementia with Lewy Body (DLB)

There are 3 core features, and visual hallucinations are a very important feature of DLB, which may not be seen in CBD.

Vascular Dementia

It is a very important differential diagnosis, as CBD patients may also have a certain focal nature of symptoms. But in vascular dementia, in imaging, certain abnormalities will be seen, such as infarction, while no such abnormality will be seen in CBD.

Treatment

Treatment is the symptomatic management of these motor symptoms that we have. We already discussed that patients may not respond to Parkinsonian drugs like levodopa.

• Focal dystonia—Botulinum toxin
• Tremor: Propranolol or Primidone
• Myoclonus: Clonazepam

It has also been seen that there is an important role in various therapies, such as physical therapy, occupational therapy, and speech therapy, in patients with CBD.

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Progressive Supranuclear Palsy (PSP)

Patients usually present with progressive supra-nuclear gaze palsy, postural instability, and repeated falls and may have Parkinson's symptoms like tremors and rigidity.

Atypical Presentation

Patients may present with atypical presentations like 

• Progressive aphasia
• Symptoms of Frontotemporal dementia
• Obsessive-compulsive symptoms may also be seen.

Different clinical presentations: Richardson syndrome

Classic phenotype of PSP

• PSP: Parkinsonism
• Pure akinesia with gait freezing.
• Cerebellar ataxia

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Laboratory Examination

MRI: Morning glory sign—atrophy of midbrain tegmentum. Because of the concave appearance, there is the morning glory sign. It appears like a morning glory flower. Hummingbird sign: atrophy of the rostral brain. Seen in the mid-sagittal section. These are some signs related to PSP that you should remember.

SPECT, PET: We see frontosubcortical hypoperfusion and hypometabolism, and these findings are symmetrical.

Pathological Finding

These patients may have neurofibrillary triangles and neutrophil threads in the basal ganglia and brainstem. Tau-positive astrocytes may be seen in these areas. These are supportive of the diagnosis of PSP.

Treatment

Respond poorly to Parkinsonian treatment such as levodopa. Usually, symptomatic management is done. Various therapies, such as physical therapy, occupational therapy, and speech therapy, play important roles in the management of the patient.

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Hope you found this blog helpful for your Psychiatry residency Neurology and General Medicine preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.

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