Summary
Condition | Pathogenesis | Clinical Features | Differences |
Acute Intermittent Porphyria (AIP) | Partial deficiency of hydroxymethylbilane synthase (HMBS) increased production and excretion of porphobilinogen and θ-aminolevulinic acid from liver | Recurrent: abdominal pain, psychosis, and neuropathy (motor and autonomic). -Autonomic neuropathy leads to gastroparesis, constipation/pseudoobstruction, and autonomic instability. - Attacks may be provoked by certain drugs. - Treatment with intravenous hematin when supportive measures are inadequate or severe. | - Associated with porphyrin metabolism - Unique abdominal pain presentation |
Hereditary sensory and motor neuropathy (HSMN, Charcot-Marie-Tooth disease) | Hereditary motor and sensory neuropathy | - Progressive muscle weakness - Sensory loss - Foot deformities - Demyelination on nerve conduction studies - HSMN type I (autosomal dominant) due to defect in PMP-22 gene (codes for myelin), resulting in predominantly demyelinating neuropathy. - Features often start at puberty, with motor symptoms predominating (distal muscle wasting, pes cavus, clawed toes, foot drop, leg weakness). - HSMN type II is primarily axonal neuropathy | - Genetic inheritance - Distinct foot deformities |
Chronic Axonal Neuropathy | Axonal degeneration without demyelination | - Gradual, symmetric sensory and motor loss | - Axonal pathology without demyelination |
Multifocal motor neuropathy with conduction block (CIDP) | Acquired demyelination - Affects proximal portions of nerves where they exit the spinal cord (nerve roots). | - Gradually progressive weakness - Large-fiber sensory and motor disturbances - Areflexia - Onion-bulb formation | - Acquired demyelination - Onion-bulb formation Similar to Guillain-Barré syndrome (acute inflammatory demyelinating polyneuropathy, AIDP), but progresses slowly or remits rather than having an acute onset. - Patients experience proximal and distal weakness and sensory loss from the onset. - Raised CSF protein may be present due to inflammation affecting nerve roots within the thecal sac. |
Diabetic Neuropathy | Nerve damage due to diabetes | - Sensory symptoms - Motor weakness - Autonomic symptoms | - Associated with diabetes - Autonomic involvement |
Hereditary Sensory and Autonomic Neuropathy | Rare genetic disorder | - Sensory loss - Pain insensitivity - Autonomic dysfunction - Foot ulcers, Charcot joints | - Rare genetic etiology - Pain insensitivity |
HIV Neuropathy | Associated with HIV infection | - Sensory symptoms - Motor weakness - Autonomic symptoms | - Associated with HIV - Autonomic involvement |
Mononeuritis Multiplex | Multiple isolated nerve lesions | - Asymmetric weakness - Sensory loss - Pain | individual nerves are transiently disabled over the course of minutes to days, and the recovery of function may require weeks to months. Diabetes is the commonest cause. |
Multifocal motor neuropathy with conduction block | Asymmetric weakness, conduction block | - Younger to middle-aged men develop focal arm weakness in the distribution of a named nerve rapidly (e.g., within a week). - Over several months, additional named motor nerves become involved asymmetrically, resembling MND | MMNCB shows conduction block due to segmental demyelination; MND does not - Nerve conduction studies help determine if a motor neuropathy is axonal or demyelinating. - Anti-GM1 antibodies may be present. |
Paraneoplastic Neuropathy | Associated with malignancies | - Sensory and motor symptoms - May precede cancer diagnosis | - Associated with cancer - May be a paraneoplastic syndrome |
Paraproteinemic Neuropathy | Associated with monoclonal gammopathy | - Sensory symptoms - Weakness - Demyelination on nerve conduction studies | - Associated with monoclonal gammopathy - Demyelination |
Sarcoidosis | Granulomatous inflammatory disease | - Sensory and motor symptoms Affects both central and peripheral nervous systems Presents with optic atrophy | - Associated with granulomatous inflammation optic atrophy |
Vasculitis | Inflammation of blood vessels | - Sensory and motor symptoms | - Associated with vasculitis |
Classification
Type of pathology | Definition/features | Causes/specific syndromes |
Mononeuropathy | One peripheral nerve involved | - Injury/iatrogenic - Compression/entrapment |
Polyneuropathy | Diffuse lesions of many nerves involved: - Distal nerves > prox nerves involved - Motor + sensory (incl. pain) fibers involved | - Endocrinological diseases (DM, hypothyroidism) - Alcohol - Vitamin B12 deficiency - Heavy metals - Meds (e.g., chemotherapy) - Radiotherapy - Charcot–Marie–Tooth II (CMT II) |
Mononeuritis multiplex | >2 nerves involved in non-contiguous areas (simultaneous OR sequential) | - Autoimmune diseases (systemic lupus erythematosus [SLE], RA, sarcoid) - Vasculitis (polyarteritis nodosa) |
Plexopathy | Brachial OR lumbosacral plexus involved | - Trauma - Brachial neuritis (Parsonage–Turner syndrome) |
Causes
- Hereditary (CMT disorder)
- Traumatic (injuries, entrapment)
- Infection (Hansen’s, AIDS, Guillain–Barré)
- Autoimmune (sarcoidosis, polymyalgia rheumatica)
- Ca (paraneoplastic, CTX, RTX)
- Metabolic (hypothyroidism, DM, uremic neuropathy, amyloid)
- Medicines, toxins (heavy metals), alcohol
- Vitamin B12 deficiency
- Pseudoneuropathy
Peripheral neuropathy vs radiculopathy
Feature | Radiculopathy | Neuropathy |
Sensory distribution | Fuzzy | Discrete |
Muscle atrophy | No (rare) | Yes |
- Utilize patterns of innervation to differential diagnosis
- Sensory nerve distribution
- Motor innervation
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