MEDICAL CASE PRESENTATION

PATIENT DEMOGRAPHICS

CHIEF COMPLAINTS

1. Episodic dizziness - 2 years duration
2. Dysphagia - 2 years duration
3. Gait ataxia / imbalance - 1 year duration

HISTORY OF PRESENT ILLNESS

• Onset: Insidious
• Progression: Gradual and progressive
• Nature: Episodic
• Aggravating factors: None (NOT worsened by neck movement or positional change)
• Associated symptoms: Absent nausea/vomiting, no hearing impairment, no tinnitus
• Relief: Partial relief with over-the-counter medications

• Gradual in onset, progressive, increasing in severity
• Associated with nasal regurgitation and dysphonia
• Severe enough to require a 3-day hospital admission
• No diurnal variation in symptoms
• Partial relief with treatment

• Progressive in nature
• Initially able to walk 100 meters; now sways laterally while walking on a flat even surface
• Adopts a broad-based gait as a compensatory strategy
• Notices imbalance while washing face with eyes closed
• Imbalance worsens with eye closure and in darkness (positive Romberg sign)

• No pins-and-needles sensation in the feet while walking
• No slippage of footwear while walking
• No difficulty with fine motor tasks (buttoning/unbuttoning clothing)
• No difficulty rising from a sitting position
• Normal bladder and bowel function

PAST HISTORY

• One prior hospital admission (3 days) for severe dysphagia
• No significant past medical history documented

DRUG HISTORY

• Nil current regular medications

FAMILY HISTORY

• No family history of similar illness or neurological disease

EXAMINATION FINDINGS

General Examination

• Young adult female; no acute distress at rest

Higher Mental Functions (HMF)

• Normal - orientation, memory, judgment, and cognition intact

Cranial Nerves

Motor System

Sensory System

• No sensory deficit on clinical examination
• No pin-prick or proprioceptive deficits elicited at bedside

Cerebellar Signs

• Positive cerebellar signs (dysdiadochokinesia, dysmetria - implied by positive cerebellar sign)
• Romberg's test: POSITIVE - sways towards the left

Gait

• Broad-based gait
• Lateral sway

Autonomic

• Bladder and bowel function normal

INVESTIGATIONS

CLINICAL LOCALIZATION SUMMARY

• Cerebellar ataxia (gait ataxia, cerebellar signs, gaze-evoked nystagmus, Romberg positive)
• Sensory neuropathy (diminished SAP on NCV, absent ankle reflex)
• Bulbar dysfunction (oropharyngeal dysphagia, nasal regurgitation, dysphonia)

DIFFERENTIAL DIAGNOSIS

1. CANVAS Syndrome (Top Differential)

• Progressive cerebellar ataxia
• Sensory neuropathy (reduced SAP on NCV)
• Gaze-evoked nystagmus with vestibular involvement
• Romberg positive, worsening with eye closure
• No family history (autosomal recessive - RFC1 biallelic repeat expansion)
• Normal MRI early in the disease is characteristic

2. Multiple Sclerosis (MS) - Relapsing Remitting (RRMS)

• Episodic onset after URTI (suggesting possible relapse trigger)
• Multi-focal involvement: cerebellar + brainstem + possibly upper motor neuron (extensor plantar, brisk reflexes)
• Bilateral extensor plantars suggesting corticospinal tract involvement
• Horizontal nystagmus and internuclear ophthalmoplegia (INO) may mimic or co-exist
• Normal NCCT (MS is white matter disease - MRI with gadolinium required)

3. Spinocerebellar Ataxia (SCA) - Autosomal Recessive Types

• Friedreich Ataxia (FA): Progressive cerebellar ataxia + sensory neuropathy (absent ankle reflex is classic) + upper motor neuron signs (extensor plantars). Typically onset in teens-20s. Dysphagia occurs later in disease. No family history - but FA is autosomal recessive, meaning parents may be carriers without symptoms.
  • Key finding here: Diminished right ankle reflex + bilateral extensor plantar - this combination is classic for FA.
  • Normal B12 argues against nutritional cause.
  • Pending: GAA triplet repeat expansion in **FXN gene (frataxin)*.
• SCA types 3/6: Can present with ataxia + neuropathy + vestibular involvement (SCA 6 is characteristically ataxia + nystagmus). Usually autosomal dominant - no family history here makes this less likely but does not exclude de novo mutation or reduced penetrance.

4. Paraneoplastic Cerebellar Degeneration (PCD)

• Subacute progressive ataxia, nystagmus, dysphagia, and dysarthria in a young-to-middle-aged female raises paraneoplastic suspicion
• Anti-Yo (anti-Purkinje cell antibodies) in breast/ovarian cancer; anti-Hu, anti-Ri antibodies in lung/breast tumors
• The progressive nature, female sex, and multi-system involvement are characteristic
• Bulbar involvement (dysphagia, dysphonia) is well described in paraneoplastic brainstem encephalitis
• Harrison's (2025) notes: "dysphagia, dysarthria, gait and limb ataxia, variable downbeating nystagmus, brainstem dysfunction, or upgoing toes" in PCD

5. Autoimmune Brainstem Encephalitis / Anti-GABA-B / Anti-DPPX Encephalitis

• Subacute cerebellar + bulbar dysfunction + nystagmus in a young female
• Anti-GABA-B receptor antibodies classically produce cerebellar ataxia + limbic features
• Anti-DPPX may cause brainstem + cerebellar dysfunction with autonomic features
• No cognitive impairment here, but early phases may be purely cerebellar/brainstem

6. Posterior Fossa Lesion / Arnold-Chiari Malformation

• Episodic dizziness after URTI, progressive ataxia, horizontal nystagmus, and dysphagia can all result from a posterior fossa structural lesion
• NCCT is normal - but NCCT misses subtle posterior fossa pathology (beam hardening artifact)
• MRI brain is mandatory to exclude Chiari malformation, posterior fossa tumors, and demyelinating plaques

7. Vertebrobasilar / Posterior Circulation TIA or Vasculitis

• Young married female with episodic dizziness triggered post-URTI: consider vasculitis or hypercoagulable state (anti-phospholipid syndrome)
• Episodic nature of dizziness, absence of hearing loss and tinnitus, bulbar signs, and cerebellar signs without position-dependence can suggest posterior circulation ischemia
• Less likely given 2-year progressive course without stroke-like episodes
• However, recurrent small posterior fossa infarcts can mimic progressive neurodegeneration

SUMMARY TABLE OF DIFFERENTIALS

RECOMMENDED NEXT INVESTIGATIONS (Priority Order)

1. MRI Brain + Spine with Gadolinium - single most important next step (rules out MS, Chiari, posterior fossa tumor, cerebellar atrophy pattern)
2. Anti-neuronal antibody panel (serum + CSF) - paraneoplastic and autoimmune encephalitis screen
3. RFC1 repeat expansion - CANVAS
4. FXN GAA repeat expansion - Friedreich Ataxia
5. CSF analysis - cell count, protein, glucose, oligoclonal bands
6. Vestibular function tests - video Head Impulse Test (vHIT), caloric testing
7. Anti-phospholipid antibody panel / vasculitis screen (ANA, ANCA, dsDNA, APL)
8. Tumor markers + CT chest/abdomen/pelvis - paraneoplastic screen
9. Genetic panel for SCA (if above are negative)

Key clinical teaching point: The combination of bilateral extensor plantar responses + absent ankle reflex + cerebellar ataxia + sensory neuropathy is the hallmark triad of Friedreich Ataxia or CANVAS. The added bulbar involvement (dysphagia + nasal regurgitation + dysphonia) expands the differential to include paraneoplastic disease and MS with brainstem involvement. MRI brain and spine with contrast is the single most urgent next step given a normal NCCT does not rule out white matter disease or posterior fossa pathology.