Cerebellum pathologies
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Cerebellum Pathologies
Anatomy & Functional Zones (Brief Recap)
The cerebellum is organized into three functional zones, each with distinct clinical implications when damaged:
| Zone | Input/Function | Lesion Effects |
|---|---|---|
| Vestibulocerebellum (flocculonodular lobe) | Balance, vestibulo-ocular reflex | Truncal ataxia, gait instability, nystagmus |
| Spinocerebellum (vermis + intermediate hemisphere) | Limb coordination, posture | Gait ataxia, ipsilateral limb dysmetria |
| Cerebrocerebellum (lateral hemispheres) | Planning & timing of voluntary movement | Appendicular ataxia, intention tremor, dysarthria |
I. Clinical Features of Cerebellar Disease
From Adams and Victor's Principles of Neurology (12th ed.), cerebellar lesions produce a recognizable constellation:
- Ataxia - incoordination of volitional movement; decomposition of smooth sequences into irregular, jerky components ("decomposition of movement" per Holmes)
- Intention tremor - side-to-side oscillation as the limb approaches a target (also called ataxic tremor)
- Dysmetria - undershooting or overshooting a target; failure of the normal ballistic agonist-antagonist-agonist triphasic sequence
- Dysdiadochokinesis - impaired rapid alternating movements (adiadochokinesis, per Babinski)
- Dysarthria - scanning/staccato speech from incoordination of articulation muscles
- Gait and equilibrium disorders - wide-based, truncal instability
- Hypotonia - particularly with acute cerebellar lesions
- Nystagmus - impaired ocular pursuit, inaccurate saccades
Lesions of one cerebellar hemisphere cause ipsilateral ataxia (due to double-crossing of pathways). Cognitive effects - including frontal-type dysexecutive syndrome - can occur with cerebellar disease ("cerebellar cognitive affective syndrome").
II. Vascular Pathologies
Cerebellar Hemorrhage
(Plum and Posner's Diagnosis and Treatment of Stupor and Coma)
About 10% of intraparenchymal hemorrhages occur in the cerebellum. Classic presentation:
- Sudden occipital headache, nausea/vomiting, vertigo
- Truncal and gait ataxia, dysarthria
- Nystagmus, ipsilateral gaze paralysis
- Ipsilateral facial palsy, contralateral extensor plantar response
Causes: hypertension (~75%), cerebellar angiomas, anticoagulants, amyloid angiopathy in the elderly. Hypertensive hemorrhages arise near the dentate nuclei. The hemorrhage can cause coma by compressing the brainstem - early diagnosis is critical as surgical evacuation can be life-saving; once the patient is comatose, mortality is high despite intervention.
Cerebellar Infarction
Accounts for ~2% of all strokes. Symptoms resemble hemorrhage but progress more slowly (edema over 2-3 days). Key features:
- Acute/subacute vertigo, dizziness, unsteadiness, dull headache
- Nystagmus toward the infarct, ipsilateral dysmetria
- Risk factors: hypertension, atrial fibrillation, hypercholesterolemia; vertebral artery dissection in younger patients
A mass effect from edema can compress the brainstem and fourth ventricle, requiring urgent surgical decompression. From the admission data of 293 patients: vertigo/dizziness (70%), limb ataxia (59%), truncal ataxia (45%), dysarthria (42%), nystagmus (38%).
III. Tumors
Medulloblastoma (WHO Grade IV)
(Bradley and Daroff's Neurology in Clinical Practice)
- Most common malignant brain tumor in children (>50% under age 10); second peak at 18-25 years
- Arises from external granular layer or subependymal matrix cells of the fourth ventricle
- Small immature cells with hyperchromatic nuclei, numerous mitoses, Homer Wright rosettes
- High propensity to invade the fourth ventricle and disseminate along CSF pathways
- 5-year survival: 70-80% with current treatment
Molecular subgroups (WHO 2016):
- WNT-activated (best prognosis; CTNNB1 mutations)
- SHH-activated (linked to Gorlin syndrome / PTCH mutations on 9q)
- Group 3 and Group 4 (less favorable)
Histological variants: classic, anaplastic/large-cell (worst prognosis), desmoplastic/nodular (better prognosis, associated with Gorlin syndrome in lateral hemispheres).
Hemangioblastoma (WHO Grade I)
(Bradley and Daroff's Neurology in Clinical Practice)
- Most common primary cerebellar neoplasm in adults
- Benign vascular tumor; peak frequency at age 40; more common in males
- Classic appearance: cyst with an enhancing mural nodule
- Rich vascular supply (dark red) - predisposes to spontaneous hemorrhage
- ~10% associated with von Hippel-Lindau (VHL) disease (VHL gene at 3p25-26)
- Histology: abundant capillaries + foamy lipid-laden stromal cells (stain with inhibin, S100, brachyury)
- Can also occur in retina, brainstem, spinal cord (especially in VHL)
IV. Degenerative / Hereditary Diseases
Friedreich's Ataxia
The most common autosomal recessive cerebellar ataxia. Caused by GAA trinucleotide repeat expansion in the frataxin gene on chromosome 9. Features include:
- Progressive cerebellar ataxia (gait onset, then limbs)
- Absent tendon reflexes, positive Babinski sign
- Loss of proprioception and vibration sense (dorsal column involvement)
- Dysarthria, nystagmus
- Cardiomyopathy (major cause of death), kyphoscoliosis, pes cavus
Spinocerebellar Ataxias (SCAs)
A family of autosomal dominant disorders caused by various genetic mutations (most commonly CAG/polyglutamine repeat expansions). Over 40 types identified. Shared features: progressive cerebellar ataxia, often with variable brainstem, spinal cord, and extrapyramidal involvement. SCA3 (Machado-Joseph disease) is the most common worldwide.
Multiple System Atrophy - Cerebellar type (MSA-C)
(Adams and Victor's Principles of Neurology, formerly olivopontocerebellar atrophy / OPCA)
- Sporadic, progressive; mean age of onset ~6th decade
- Degeneration of pontocerebellar and olivocerebellar fibers, middle cerebellar peduncles, cerebellar white matter
- Loss of Purkinje cells variable
- MRI: vermian atrophy + smallness of the pons ("hot cross bun" sign)
- Autonomic failure (urinary dysfunction, erectile dysfunction) and REM sleep behavior disorder are prominent
- Often associated with extrapyramidal features (parkinsonism)
Alcoholic Cerebellar Degeneration
(Adams and Victor's Principles of Neurology)
- Pathologically related to Wernicke's disease (thiamine deficiency); predominantly anterior vermis degeneration
- Clinically dominated by gait ataxia; arm ataxia is less prominent
- Characteristic that limb tremor is less marked than in paraneoplastic or familial types
- Progresses with continued alcohol use; partial improvement with thiamine and abstinence
V. Paraneoplastic Cerebellar Degeneration (PCD)
(Adams and Victor's Principles of Neurology; Bradley and Daroff's Neurology)
One of the most characteristic paraneoplastic syndromes.
Associated tumors:
- Small cell lung carcinoma (SCLC) - ~1/3 of cases
- Ovarian carcinoma - ~25%
- Hodgkin lymphoma - ~15%
- Breast, bowel, uterine carcinomas
Key antibodies:
| Antibody | Associated Cancer |
|---|---|
| Anti-Yo (PCA-1) | Breast, gynecological |
| Anti-Hu | SCLC (with PEM) |
| Anti-VGCC | SCLC (also with Lambert-Eaton) |
| Anti-Tr (anti-DNER) | Hodgkin lymphoma |
| Sox1 | SCLC (~50% of PCD cases) |
| Anti-Ki | Breast, gynecological, SCLC |
Clinical features:
- Subacute onset (weeks-months) of symmetric pancerebellar dysfunction - gait and limb ataxia, dysarthria, nystagmus
- In >50% of cases, cerebellar signs precede tumor diagnosis
- May also have vertigo, diplopia, Babinski signs, sensorineural hearing loss, cognitive changes
- CSF: mild pleocytosis, elevated protein possible
- FDG-PET shows cerebellar hypometabolism before MRI changes
Prognosis: Poor due to irreversible Purkinje cell loss; most patients do not improve with immunotherapy (IVIG, plasma exchange, rituximab, corticosteroids). Early tumor treatment is paramount.
VI. Other Notable Cerebellar Pathologies
| Condition | Key Features |
|---|---|
| Cerebellar abscess | Usually from otogenic/sinogenic source or hematogenous spread; subacute fever + cerebellar signs + raised ICP |
| Multiple sclerosis | Demyelinating plaques in cerebellar peduncles or white matter; intention tremor, INO, ataxia; relapsing-remitting course |
| Cerebellar hypoplasia | Congenital underdevelopment; may be isolated or part of syndromes (Dandy-Walker, Joubert syndrome) |
| Cerebellar abscess | Post-infectious or direct extension; urgently requires drainage |
| Anti-GAD ataxia | Autoimmune; associated with anti-GAD65 antibodies; downbeat nystagmus prominent |
| Celiac-related ataxia (gluten ataxia) | Subacute cerebellar syndrome associated with anti-gliadin/anti-transglutaminase antibodies; responds to gluten-free diet |
| Hypothyroidism | Reversible cerebellar ataxia; slow movements, gait unsteadiness |
| Drug/toxin-induced | Phenytoin, carbamazepine, lithium, alcohol, heavy metals; often reversible |
VII. Differential Diagnosis Summary
Cerebellar ataxia must be distinguished from:
- Sensory ataxia (posterior column/large fiber neuropathy) - worsened by eye closure, Romberg positive, proprioception lost, no dysarthria/nystagmus
- Vestibular ataxia - rotatory nystagmus, past-pointing toward one side
- Frontal lobe ataxia - gait apraxia, cognitive features prominent
- Miller Fisher syndrome - post-infectious; ataxia + ophthalmoplegia + areflexia (anti-GQ1b)
Sources: Adams and Victor's Principles of Neurology (12th ed.) | Bradley and Daroff's Neurology in Clinical Practice | Plum and Posner's Diagnosis and Treatment of Stupor and Coma | Robbins & Kumar Basic Pathology | Harrison's Principles of Internal Medicine (22nd ed., 2025)
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