Peripheral Neuropathy Flashcards
What sensory modalities are carried in the “large fibres”?
Joint position and vibration sense
What sensory modalities are carried in the dorsal columns?
Proprioception and vibration, fine touch and 2-point discrimination
What sensory modalities are carried in the small fibres?
Pain and temperature (spinothalamic tracts)
Autonomic function
What sensory modalities are carried in the spinothalamic tracts?
Pain, temperature and crude touch
When diagnosing a peripheral neuropathy, what are important factors to consider?
- If it is sensorimotor, motor or sensory
- If sensory, if it is small or large fibre
- Is there any autonomic involvement? Features suggestive of autonomic dysfunction include resting tachycardia and postural BP drop
What skin changes may be associated with a peripheral neuropathy?
- Dry
- Thin
- Atrophic
- Hypopigmentation
- Loss of hair
- Callosities and ulcer formation (associated diseae)
- Signs of chronic infection
What are Charcot’s joints? (neuropathic joints)
Swollen, deformed joints with abnormal ROM.
Siggest loss of pain and proprioception
May have crepitus
Ankle and elbow joints most commonly affected, but may affect any joint
How would a motor neuropathy manifest?
LMN pattern with distal-to-proximal gradient (longest fibres affected first)
Affects upper limbs once disease reaches the knee
Where should you look for wasting in a motor neuropathy?
Upper limb- first dorsal interossei (between thumb and first finger).
Small muscles of hands with dorsal guttering and MCP hypertextension and IP joint flexion deformities
Lower limb- tibialis anterior
What pattern of sensory loss would you expect in a peripheral sensory neuropathy?
Glove and stocking distribution
Usually symmetrical ascending pattern of loss- upper limbs only usually affected once sensory loss reaches the knees.
May not affect all sensory modalities
What types of gait would be suggestive of a peripheral neuropathy?
High steppage gait
Wide based gait
What would a high steppage gait suggest?
Loss of proprioception at the ankle (sensory large fibre loss) and/or foot drop (motor neuropathy)
What type of peripheral neuropathy would be suggested by a wide-based gait?
Sensory- patients often watch the gound as the walk to use visual input to compensate for loss of proprioception
What test that can be carried out on examination would you expect to be positive in a patient with a sensory neuropathy?
Romberg’s- standing with feet together and shutting eyes –> unsteadiness
Stand close to the patient and support them!
What are the common causes of a sensorimotor neuropathy?
- Common:
- ETOH
- DM
- Drugs:
- Chemotherapeutic (vincristine, paclitaxel, cisplatin),
- Rheum drugs (gold, allopurinol
- Endocrine: Hypothyroidism
- Vascular: Vasculitis
- Acquired: CIDP/GBS
- Metabolic: Uraemia
- Neoplastic: Paraneoplastic syndrome
- Congenital:
- Hereditary motor and sensory neuropathies
What are the common causes of a motor neuropathy?
(FYI none are really common)
- CIDP/GBS
- Drugs: Dapsone
- Porphyria
- Lead poisoning
- Infections: Diphtheria
What are the common cause of a sensory neuropathy?
- ETOH
- DM
- Vitamin B12 deficiency
- Infections e.g. leprosy, Lyme disease, HIV
- Drugs e.g. colchicine, disulfiram, isoniazid
- Hypothyroid
- Flecainide
What are the causes of an autonomic neuropathy?
- GBS
- DM
- HIV
- Rarer: Paraneoplastic, amyloid
- Stupidly rare: Porphyria, botulism, Chagas
What are the causes of a small fibre neuropathy?
- DM
- ETOH
- Infections: HIV, leprosy
- Endocrine: Hypothyroidism
- Autoimmune: Sjogrens, PBC
- Drugs e.g. cisplatin, isoniazid
- Heavy metals e.g. gold, arsenic
What is a small fibre neuropathy?
Subtype of peripheral neuropathy where the small caliber sensory nerve fibres (A-delta fibres- cold, pain, autonomic) and umyelinated C fibres (warmth) are affected.
What are the causes of demyelinating polyneuropathies?
- HIV
- Haem:
- Multiple myeloma
- MGUS
- Neuro:
- Hereditary motor and sensory neuropathy
- Chronic inflammatory demyelinating polyneuropathy
- Refsums disease
How would you investigate a patient with peripheral neuropathy?
- Bedside:
- Urine dip: Glucose, send urine for bence jones proteins
- Bloods:
- FBC: Thyroid, vitamin deficiencies, haem causes
- ESR: Vasculitis, inflammatory process
- Us&Es:
- LFTs
- Glucose: DM
- TFTs:
- Serum B12 and folate
- Serum protein electrophoresis
- Autoimmune profile
- Further testing:
- Nerve conduction studies
- LP- CSF analysis
- Autonomic function tests (e.g. lying and standing BP?)
- Nerve biopsy
- Genetic testing
What is mononeuritis multiplex?
Painful asymmetrical sensorimotor neuropathy (may become symmetrical with disease progression)
Damage to at least two peripheral nerve areas
What are the causes of mononeuritis multiplex?
- DM
- Rheum:
- SLE
- RA
- Sjogren’s
- Vasculitides:
- Churg Strauss
- Wegener’s
- PAN
- Neoplastic: Lymphoma, carcinoma
- Infectious: Lyme disease, leprosy
- Sarcoid, amyloid
What conditions cause thickening of the peripheral nerves?
- Hereditary motor and sensory neuropathy
- Leprosy
- Neurofibromatosis
- Amyloidosis
- Acromegaly
How would you manage a patient with a peripheral neuropathy?
Depends on cause. MDT approach- GP, neurologist, specialist nurses, physio, OT
- Conservative:
- Foot care and shoe advice
- Joint splinting- may prevent contractures
- Avoid ETOh and other precipitants
- Medical:
- Optimise glycaemic control
- Replace nutritional deficiencies
- Vasculitis- steroids, immunosuppression
- Analgesia: Neuropathic pain- amitriptyline, gabapentin
- GBS: IVIG
