The Most Common Hereditary Ataxia
Key Features
Critical Must-Knows
- FXN Gene: GAA trinucleotide repeat expansion.
- Cardiomyopathy: Leading cause of death.
- Scoliosis: Progressive, often requires fusion.
- Cavovarus Feet: Common, similar to CMT.
- Wheelchair Dependency: Usually by 15 years after onset.
Clinical Pearls
- "GAA repeat in FXN gene
- "Cardiomyopathy is main mortality cause
- "Scoliosis surgery has cardiac risks
- "Similar foot deformity to CMT
Critical Cardiac Risks in Friedreich Ataxia
Leading Cause of Death
Hypertrophic Cardiomyopathy is the main cause of mortality. Sudden cardiac death can occur. Arrhythmias and heart failure are common.
Pre-Op Mandatory
Cardiology Clearance with recent Echocardiogram and ECG is ESSENTIAL before any orthopaedic surgery (especially scoliosis fusion).
Anesthesia Alert
Anesthesia team must be aware of cardiomyopathy. Fluid management (preload maintenance) is critical to prevent cardiac decompensation.
Friedreich Ataxia vs CMT
| Feature | Friedreich Ataxia | CMT |
|---|---|---|
| Autosomal Recessive | Autosomal Dominant (usually) | |
| Spinocerebellar | Peripheral nerve | |
| Cardiomyopathy (major) | Not affected | |
| 80-100% | Rare | |
| Cavovarus | Cavovarus |
FACSFriedreich Ataxia Features
| F | FXN Gene Frataxin deficiency |
| A | Ataxia Progressive gait and limb ataxia |
| C | Cardiomyopathy Hypertrophic, leading cause of death |
| S | Scoliosis 80-100%, often progressive |
| F | FXN Gene Frataxin deficiency | C | Cardiomyopathy Hypertrophic, leading cause of death |
| A | Ataxia Progressive gait and limb ataxia | S | Scoliosis 80-100%, often progressive |
Hook:FACS - FXN, Ataxia, Cardiomyopathy, Scoliosis.
SFOrthopaedic Issues
| S | Scoliosis Progressive, often needs fusion |
| F | Feet Cavovarus deformity |
| S | Scoliosis Progressive, often needs fusion |
| F | Feet Cavovarus deformity |
Hook:SF - Spine and Feet.
CRDPre-Op Checklist
| C | Cardiac Echo and cardiology review |
| R | Respiratory PFTs if needed |
| D | Diabetes Check glucose |
| C | Cardiac Echo and cardiology review |
| R | Respiratory PFTs if needed |
| D | Diabetes Check glucose |
Hook:CRD - Cardiac, Respiratory, Diabetes.
Overview/Epidemiology
Friedreich Ataxia (FA) is the most common hereditary ataxia.
- Genetics: Autosomal recessive. GAA trinucleotide repeat expansion in the FXN gene on chromosome 9.
- Incidence: 1 in 50,000.
- Onset: Usually 5-15 years. Earlier onset = more severe.
- Pathophysiology: Frataxin deficiency leads to mitochondrial dysfunction and iron accumulation in cells.
Pathophysiology
Neurological Pathology
- Degeneration of spinocerebellar tracts, dorsal columns, and peripheral nerves.
- Results in ataxia, sensory loss, and weakness.
- Pyramidal signs late (Babinski positive despite absent reflexes).
Why Scoliosis Develops
- Combination of truncal weakness and ataxia.
- Curve patterns variable (unlike neuromuscular scoliosis).
- Often progresses rapidly, especially in wheelchair users.
Cavovarus Feet
- Similar mechanism to CMT (muscle imbalance).
- May precede neurological symptoms.
Classification Systems
Neurological Features
- Gait Ataxia: Often the first symptom. Progressive.
- Limb Ataxia: Intention tremor, dysmetria.
- Dysarthria: Slurred speech.
- Reflexes: Absent tendon reflexes with positive Babinski.
- Sensory Loss: Proprioception and vibration affected.
- Wheelchair Dependency: Usually by 10-15 years after onset.
Clinical Assessment
History:
- Age of onset.
- Progression of ataxia.
- Cardiac symptoms (palpitations, syncope).
- Family history.
- Mobility status.
Physical Exam:
- Gait: Wide-based, ataxic.
- Reflexes: Absent with positive Babinski.
- Sensory: Reduced proprioception, vibration.
- Spine: Scoliosis assessment.
- Feet: Cavovarus, claw toes.
- Cardiac: Listen for murmurs.
Investigations
Genetic Testing:
- FXN gene GAA repeat expansion: Confirmatory.
Cardiac:
- Echocardiogram: Assess for hypertrophic cardiomyopathy.
- ECG: Arrhythmias.
Metabolic:
- HbA1c, glucose: Diabetes screening.
Imaging:
- Spine X-ray: Scoliosis.
- Foot X-ray: Cavovarus assessment.
Management Algorithm
Scoliosis Management
- Observation: For mild curves.
- Bracing: May slow progression but does not prevent it.
- Surgery: Posterior spinal fusion for curves greater than 40-50 degrees.
- Cardiac Clearance: Essential before surgery.
Surgical Techniques
Posterior Spinal Fusion
Indications: Progressive scoliosis greater than 40-50 degrees.
Pre-op: Cardiology clearance mandatory. Echocardiogram. Anesthesia team experienced with cardiomyopathy.
Technique: Posterior approach. Fusion extent depends on curve (often T2-L4 or pelvis if sitting). Pedicle screw constructs.
Post-op: ICU monitoring. High perioperative risk due to cardiac disease.
Complications
| Complication | Context | Management |
|---|---|---|
| Cardiac Arrhythmia/Sudden Death | Intra/postoperative | Cardiac monitoring, experienced team |
| Respiratory Compromise | Surgery, disease progression | Careful anesthesia, postop monitoring |
| Scoliosis Progression | Even after fusion at end of construct | Monitor |
| Foot Deformity Recurrence | Progressive disease | Monitor, revise |
Postoperative Care
- ICU Monitoring: Cardiac telemetry.
- Early Mobilization: As tolerated.
- Physiotherapy: Maintain function.
- Long-Term: Cardiology follow-up, orthotic use.
Outcomes/Prognosis
- Life Expectancy: Median 30-40 years. Cardiac disease is the main determinant.
- Wheelchair Dependency: Usually 10-15 years after symptom onset.
- Scoliosis Surgery: Improves sitting, may prevent respiratory decline.
- Disease Progression: Relentless. No cure currently.
Evidence Base
- Identified the X25 (FXN) gene at 9q13 encoding the 210-amino-acid mitochondrial protein frataxin
- Most patients are homozygous for an unstable GAA triplet-repeat expansion in the first FXN intron; a minority carry point mutations
- Established the molecular basis for confirmatory genetic testing in this autosomal recessive disease
- Of 56 patients with typical FA, all had scoliosis over 10 degrees; double thoracic-and-lumbar curves were most common (57%) and patterns did not resemble idiopathic curves
- Curve behaviour was bimodal: curves over 60 degrees progressed, whereas curves of 40 degrees or less tended to remain stable
- Progression related more to age at onset and curve magnitude than to neurological severity
- Scoliosis occurred in 49 of 77 FA patients (63%); 33% had double-major curves and patterns were variable
- Bracing gave poor results (mean progression 15 degrees in brace); 33% ultimately underwent fusion, most while wheelchair-dependent
- SSEP neuromonitoring was effective in only 1 of 11 cases — preparation for a wake-up test is recommended
- Single-centre series of 17 FA adolescents undergoing posterior spinal fusion; 100% had hypertrophic cardiomyopathy with preserved systolic function
- Postoperative complications were very high (88%), ranging from nausea/vomiting to hypotension/tachycardia (29%) and one ECMO requirement
- Baseline neuromonitoring was poor in 4 patients and lost in 1, prompting wake-up tests in 24%
- International double-blind placebo-controlled phase 2 RCT; 103 randomised (omaveloxolone 51, placebo 52), full analysis 40 vs 42
- At 48 weeks mFARS improved with omaveloxolone (-1.55) versus placebo (+0.85), a between-group difference of -2.40 points (p = 0.014)
- Transient reversible aminotransferase rises, headache, nausea and fatigue were the main adverse effects
- Synthesises FA as a multisystem disorder of nervous system, heart, musculoskeletal system and metabolism driven by frataxin deficiency
- Reaffirms cardiomyopathy as the leading cause of mortality, with scoliosis and diabetes as common extraneural features
- Frames omaveloxolone approval (FDA, EMA) as a milestone while genotype-phenotype heterogeneity remains incompletely explained
Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scoliosis in Friedreich Ataxia
"12-year-old with confirmed Friedreich Ataxia. Thoracolumbar scoliosis of 55 degrees. Ambulant with assistance. Known hypertrophic cardiomyopathy on echo."
This patient needs **scoliosis surgery** given the 55-degree curve and progressive disease. However, the **cardiomyopathy is a major concern**. Pre-operatively, I would ensure **cardiology clearance** with recent echo and ECG. The anesthesia team must be experienced in managing cardiomyopathy (avoid hypovolemia, maintain preload). I would perform **posterior spinal fusion** (likely T2-L4 or lower depending on curve). Postoperatively, **ICU monitoring with telemetry** is essential. I would counsel the family about the increased surgical risk.
Cavovarus Feet in FA
"Same patient also has bilateral cavovarus feet with claw toes. Coleman block test is positive."
The cavovarus feet are managed similarly to CMT. The **positive Coleman block test** indicates the deformity is **supple**. I would perform **soft tissue surgery**: plantar fascia release, first metatarsal dorsiflexion osteotomy, peroneus longus to brevis transfer, and claw toe correction (Jones procedure). Given the progressive nature of FA, recurrence is possible. Post-op orthotic use is important.
Genetics of FA
"What is the genetic cause of Friedreich Ataxia?"
Friedreich Ataxia is caused by a **GAA trinucleotide repeat expansion** in the **FXN gene** on chromosome 9. This gene encodes **frataxin**, a mitochondrial protein. Frataxin deficiency leads to iron accumulation and mitochondrial dysfunction, causing cell death particularly in the nervous system and heart. The inheritance is **autosomal recessive**.
MCQ Practice Points
Genetics MCQ
Q: What is the genetic mutation in Friedreich Ataxia? A: GAA trinucleotide repeat expansion in the FXN gene.
Cardiac MCQ
Q: What cardiac condition is most associated with FA? A: Hypertrophic cardiomyopathy.
Orthopaedic MCQ
Q: What percentage of FA patients develop scoliosis? A: 80-100%.
Prognosis MCQ
Q: What is the leading cause of death in FA? A: Cardiac disease (cardiomyopathy, arrhythmias).
Neurological MCQ
Q: What is the unique reflex finding in FA? A: Absent deep tendon reflexes with positive Babinski sign (pyramidal signs with peripheral neuropathy).
Scoliosis Surgery MCQ
Q: What is essential before scoliosis surgery in FA? A: Cardiology clearance with echocardiogram and ECG to assess cardiomyopathy.
Guidelines, Registries & Global Practice
Global Epidemiology
- Most common inherited ataxia in populations of European, Middle Eastern, South Asian and North African descent; prevalence roughly 1 in 50,000, carrier frequency around 1 in 60-90.
- Effectively absent in populations of Sub-Saharan African and East Asian origin — a useful exam discriminator pointing away from FA.
- Larger GAA expansions broadly correlate with earlier onset, more frequent cardiomyopathy and diabetes, and faster progression to wheelchair use.
Side-by-Side Practice
| Body / Region | Position Relevant to Orthopaedics |
|---|---|
| Friedreich's Ataxia clinical care guidelines (international consensus) | Endorse structured spine and cardiac surveillance; scoliosis follows magnitude/progression-based surgical thresholds rather than fixed Cobb cut-offs alone |
| AAOS / SRS (US) approach | Modern segmental pedicle-screw constructs; selective (non-pelvic) fusion when sitting/standing function is retained |
| BOA / BSCOS (UK) approach | Surgery in specialist paediatric spinal centres with formal cardiac-anaesthetic MDT pathways |
| AO Spine / EFORT (Europe) approach | Emphasis on multimodal neuromonitoring and wake-up-test readiness given unreliable SSEPs |
| FDA / EMA (pharmacology) | Omaveloxolone approved as disease-modifying therapy; does not alter surgical indications |
Registry & Resource Notes
- No dedicated arthroplasty/implant registry captures FA spinal surgery; evidence rests on single-centre and two-centre series, so outcomes data are inherently limited.
- High-resource settings: TIVA, intraoperative echocardiography, multimodal monitoring and ICU/ECMO backup.
- Limited-resource settings: prioritise cardiac risk stratification and a planned wake-up test where advanced neuromonitoring is unavailable; concentrate care in referral centres.
- Patient organisations (e.g. Friedreich's Ataxia Research Alliance, Ataxia UK) support genetic counselling and multidisciplinary care coordination.
FRIEDREICH ATAXIA
Clinical summary
GENETICS
- •FXN Gene
- •GAA repeat
- •Autosomal Recessive
- •Frataxin deficiency
CLINICAL
- •Progressive ataxia
- •Absent reflexes + Babinski
- •Cardiomyopathy
- •Diabetes
ORTHOPAEDIC
- •Scoliosis 80-100%
- •Cavovarus feet
- •Similar to CMT management
- •High surgical risk
CARDIAC
- •Hypertrophic cardiomyopathy
- •Leading cause of death
- •Arrhythmias
- •Pre-op echo mandatory
SCOLIOSIS SURGERY
- •T2-L4 or pelvis fusion
- •Cardiology clearance
- •ICU monitoring
- •High perioperative risk
PROGNOSIS
- •Median survival 30-40 yrs
- •Wheelchair by 10-15 yrs
- •No cure currently
- •Multidisciplinary care
Self-Assessment Quiz
Differential Diagnosis
Hereditary Ataxias and FA Mimics
| Condition | Inheritance / Gene | Discriminating Features | Why It Matters |
|---|---|---|---|
| AR — FXN GAA expansion | Areflexia + extensor plantars, cardiomyopathy, scoliosis, diabetes | Cardiomyopathy drives mortality and perioperative risk | |
| AD — multiple CAG/other loci | Dominant family history, preserved reflexes, cerebellar atrophy on MRI | Different genetics; usually no cardiomyopathy | |
| AR — ATM gene | Oculocutaneous telangiectasia, immunodeficiency, radiosensitivity, raised AFP | Avoid radiation; cancer surveillance needed | |
| AR — TTPA gene | FA-like phenotype with low serum vitamin E | Treatable with vitamin E supplementation | |
| Usually AD (PMP22 etc) | Length-dependent neuropathy, cavovarus, no true ataxia or cardiomyopathy | Shared cavovarus foot but different prognosis |
Key Differentiators for Friedreich Ataxia: autosomal recessive inheritance, confirmatory GAA expansion in FXN, areflexia with positive Babinski, and cardiomyopathy (effectively unique to FA among the hereditary ataxias).
Red Flags Prompting Re-evaluation: strongly asymmetric signs, a dominant-pattern family history, or atypically rapid progression should prompt consideration of an alternative diagnosis — and always check serum vitamin E, because AVED is treatable.
Controversies & Areas of Uncertainty
| Area | The Debate | Current Position |
|---|---|---|
| Timing of fusion | Labelle suggested early fusion for curves likely to progress; others favour delaying to maximise growth and lung volume | Reserve fusion for curves over 40-60 degrees that are documented to progress; do not brace as definitive treatment |
| Fusion to the pelvis | Whether to extend the construct to the pelvis in patients with pelvic obliquity | Avoid pelvic fixation in patients who retain sitting/standing function; reserve for fixed obliquity in non-ambulators |
| Neuromonitoring strategy | SSEPs are frequently unobtainable in FA; reliance on them is unsafe | Use multimodal monitoring (add transcranial MEPs) and be prepared for a wake-up test |
| Cardiac thresholds for surgery | No agreed echo cut-off that contraindicates fusion | Decisions are individualised in an MDT; preserved systolic function with HCM is not an absolute contraindication |
| Disease-modifying therapy | Omaveloxolone slows neurological decline but its effect on cardiac and skeletal disease is unproven | Approved for neurological benefit; orthopaedic deformity still requires standard surgical management |
| Foot surgery durability | Whether to favour soft-tissue balancing or bony/arthrodesis given relentless progression | Match the Coleman block result, but counsel that recurrence is likely as the disease advances |