Peripheral Neuropathy

Subacute Combined Degeneration

RF: B12 deficiency due to impaired function stomach or small bowel progressive symmetric polyneuropathy greater in legs than arms -degeneration of dorsal spinal columns results in numbness/paresthesia, impaired proprioception/vibration, and gait ataxia -peripheral neuropathy

Evaluation

Deep tendon reflexes should be assessed, as hyporeflexia suggests peripheral pathology, whereas hyperactive reflexes imply a central cause. The patient's gait should be observed, and a Romberg test (afferent sensory pathways and posterior spinal column) should be performed. Electromyography and nerve conduction studies -Electromyography and nerve conduction studies may not be necessary when the history and examination point to a clear etiology of peripheral neuropathy (eg, classic carpal tunnel syndrome) or when an underlying condition exits that can explain the clinical presentation (eg, long-standing diabetes in a patient with a mild distal symmetric polyneuropathy). Labs: glucose metabolism (fasting blood glucose, hemoglobin A1c, glucose tolerance testing), serum creatinine, thyroid-stimulating hormone, vitamin B12 level, complete blood count, erythrocyte sedimentation rate, serum protein electrophoresis, and urinalysis.

Spinal epidural abscess

Fever, severe focal back pain and neurologic deficits -caused by hematogenous spread from bacteria from a distant source, IVDA, epidural anesthesia or steroid injection, osteomyelitis continuation Rx: surgical decompression

Charcot-Marie-Tooth

Genetic disorder with loss of both motor and sensory innervation -distal weakness and sensory loss -wasting in the legs ↓ DTR -Tremor -Foot deformity with high arch (pos caves) -legs look like inverted champagne bottles Dx: EMG No treatment

Spinal Cord Compression

Isolated, symmetric lower extremity weakness and loss of sensation, UMN signs (weakness without fasciculations, hyperreflexia, Babinski sign) possible etiologies include disc herniation, abscess, and malignancy Must evaluate immediately with MRI of spine

Contralateral hemiparesis

Lesions in CNS above the pons (above the facial nucleus) can result in contralateral hemiparesis/hemianesthesia and dysarthria

Classification of peripheral neuropathy

Mononeuropathies caused by nerve entrapment or compression

Pronator drift

Relatively sensitive and specific for UMN or pyramidal/corticospinal tract disease -can accentuate pyramidal motor weakness -UMN lesions cause more weakness in supinator muscles compared to pronator muscles of upper limb -as a result the affected arm drifts downward and palm turns (pronates) toward the floor Other pyramidal signsL focal weakness, spasticity, hyperreflexia, Babinski

Axonal polyneuropathy

Symmetric distal sensory loss, w/ or w/o burning, tingling, or muscle weakness -Initial symptoms are usually in the feet as the longest nerves are affected earliest and most severe -Begin with numbness and paresthesias in toes that gradually proceed up the limb, leading to depressed ankle reflexes and atrophy of the intrinsic foot muscles --Stocking glove pattern of sensory loss, paresthesias, and sometimes burning pain in hands -Long standing diabetes is most common cause -also alcoholism, vitamin B12 deficiency, uremia Pain and dysesthesias should be treated symptomatically using agents such as gabapentin, pregabalin, or duloxetine; venlafaxine and tricyclic medications are also effective. Opioids should generally be avoided in treating peripheral neuropathy but may be considered for acute, severe pain or when other treatments have been unsuccessful.

Postherpetic neuralgia

Treatment with antiherpetic meds like acyclovir, famciclovir or valganciclovir seems to ↓ incidence of postherpetic neuralgia -Pain treated with TCA, gabapentin, pregbalin, carbamezipine, or phenytoin -topical capsaicin helpful Zoster vaccine indicated in all persons>60

Multiple Sclerosis

autoimmune demyelinating disease of CNS that primarily affects women of child bearing age in colder climates Presents with optic neuritis (painful loss of vision), diplopia, sensory defects, motor deficits, motor weakness, bowel/bladder deficiency, gait/balance problems Signs: Uhtoff phenomenon: worsening symptoms with heat -Lhermette's sign: electric shock like sensation down limbs or spine with neck flexion Exacerbation by hot weather or stress can lead to symptoms -Complete internuclear ophthalmoplegia (horizontal nystagmus of abducting eye with stationary medial eye mover) is due to demyelination of medial longitudinal fascicles Dx: oligoclonal bands seen on CSF (higher amount of antibodies comparatively, including IgG) -MRI study of choice: clusters of demyelinated axons on white matter (T2)-periventricular, juxtacortical, infratentorial, Rx: high dose steroids for exacerbations Drugs for relapse/progression -glatriamer (copolymer I)-best -Beta-INF-best -Fingolimod -Natalizumab a/w PML, worsening neurological defects -Mitoxantrone -Azathioprine -Cyclophosphamide

Polyneuropathy

diffuse, generalized, usually symmetric involvement of the peripheral nerves. -manifestation of systemic disease or exposure to a toxin or medication. -characterized as axonal or demyelinating. -Axonal polyneuropathies result from dysfunction of peripheral nerve cells and their axons, usually from metabolic or toxic causes (DM or alcohol)

Trigeminal Neuralgia

idiopathic disorder of the 5th CN resulting in severe overwhelming pain in the face -can be precipitated by chewing, touching face, or pronouncing certain words in which tongue strikes back of front teeth "knife stuck into face Rx: oxacarbamezipine or carbamazepine -gamma knife surgery or surgical decompression for refractory cases

Demyelinating polyneuropathy

initially present with motor symptoms -hereditary motor sensory polyneuropathy (Charcot-Marie-Tooth) caused by mutations in one of genes involved with maintaining structure and function of myelin -disorders with sensory deficits, distal leg weakness, and often foot deformities -Acquired demyelinating diseases present with symmetric proximal weakness like Guillan-Barre (treat with plasmanepheresis and IVIG

Carpal tunnel syndrome

median nerve compression at wrist. Paresthesias, pain, and weakness in hand and wrist. -Can radiate up forearm at times. Paresthesias worse at night or when holding a book/steering a card -Exam-sensory loss over palmar surface of first 3 digits (median nerve distribution), weakness of thumb abduction and opposition, and atrophy of thenar eminence wrist splints and glucocorticoid injections. Steroid injections help symptoms acutely, but at 1 year there is no difference in symptoms compared to those who do not receive steroid injections -Surgery should be considered for patients with severe sensory loss, hand weakness, moderate to severe electrodiagnostic findings, or failure to respond to conservative therapy.

Mononeuropathy multiplex

simultaneous involvement of 2 or more separate, noncontiguous peripheral nerves. -result of systemic disease (DM, amyloidosis, vasculitis, or sarcoidosis) -mechanism of nerve injury may be combo of compressive, ischemic, metabolic, and inflammatory factors -when successive acute involvement of individual nerves accompanied by pain, vasculitis should be suspected as cause

Bell palsy

unilateral facial muscle weakness due to acute dysfunction of the facial nerve. -can be due to HSV1, HIV, and Lyme -Paralysis of upper AND lower face distinguish Bells palsy from facial paralysis caused by stroke or intracranial lesion, which affects only lower facial muscles (sparing the forehead and eye) A/w hyperacusis and tast disturbances as CN7 is affected -corneal ulceration is compilation of 7th CN palsy as can't close eye, especially at night→dryness and ulceration Therapy: eye patching and lubrication to protect the cornea. Patients treated with glucocorticoids (such as prednisone) within 72 hours of symptom onset have improved outcomes. The benefit of antiviral therapy in treating Bell palsy has not been established.