Week 33: Neuro Pt III

This patient has median mononeuropathy, also known as carpal tunnel syndrome, a compression neuropathy of the median nerve as it traverses under the flexor retinaculum at the wrist. The median nerve provides sensation primarily to the palmar aspect of the 1st, 2nd, 3rd, and radial side of the 4th. When it is compressed, the patient experiences pain, paresthesias, and numbness in that distribution. The Tinel’s test is performed by lightly tapping the volar surface of the wrist over the median nerve. This should elicit a sensation of tingling or pins and needles in the distribution of the median nerve. Carpal tunnel syndrome is first treated with wrist splinting and initiation of a more ergonomic work environment. NSAIDs may also be helpful. If symptoms do not improve, the patient should be referred to a hand specialist who may elect to perform a carpal tunnel release procedure.

CT scan of the head (A) would be useful if there is suspicion that this patient’s symptoms are from a central process such as an acute stroke. However, his numbness is in a peripheral nerve distribution and not dermatomal. An EMG (B) is used most commonly by neurologists to confirm damage to peripheral nerves. It may be used for carpal tunnel syndrome if the symptoms do not resolve with conservative management. A variety of heavy metals are associated with a peripheral neuropathy (lead, mercury), but these require special serologic testing, not a urine drug screen (D). The patient is at risk for occupational exposures because he works in a factory; however, most heavy metal poisonings are associated with other symptoms.

Durkan’s test: reproduction of symptoms with carpal tunnel compression
Phalen’s sign: reproduction of symptoms with wrist hyperflexion
Tinel’s sign: reproduction of symptoms with percussion over carpal tunnel
Flick sign: patient reports shaking of the hand provides relief
NSAIDs, volar splint in neutral position

This patient presents with a wrist drop caused by radial neuropathy also called “Saturday Night Palsy.” The radial nerve arises from the C5-T1 roots. It controls extension of the fingers, thumb, wrist and elbow. Symptoms of radial neuropathy depend on the location of compression. Compression in the axilla (typically from improper use of crutches) causes weakness of extension at the elbow, wrist and fingers. More typically, the nerve is compressed between the humeral shaft and another hard surface and results in weakness with extension at the wrist and fingers. This typically occurs from deep sleep (often secondary to inebriation). About 90% of radial nerve mononeuropathies that occur during sleep, coma or anesthesia recover within 6-8 weeks. Patients should be placed in a wrist splint with 60 degrees of dorsiflexion to prevent atrophy and contractures.

The axillary nerve (A) causes weakness of the shoulder (deltoid) and decreased sensation over the shoulder. Median nerve neuropathy (B) causes numbness in the 1st, 2nd and 3rd digits. Ulnar nerve (D) neuropathy symptoms depend on location but do not cause weakness with extension at the wrist.

Peripheral Neuropathies
• Sciatic: buttock injury, hip dislocation, ↓ knee flexion, foot drop, rx: analgelsics, physical therapy,
• Common peroneal: proximal fibula injury, footdrop, rx: ankle splint
• Radial: crutches, wrist/finger drop, rx: wrist splint
• Ulnar: elbow injury, ↓ finger adduction/thumb grasp, 4th/5th digit paresthesias
• Lateral femoral cutaneous: inguinal ligament entrapment, upper thigh dysesthesia/numbness

The axillary nerve (A) causes weakness of the shoulder (deltoid) and decreased sensation over the shoulder. Median nerve neuropathy (B) causes numbness in the 1st, 2nd and 3rd digits. Ulnar nerve (D) neuropathy symptoms depend on location but do not cause weakness with extension at the wrist.

This patient has multiple sclerosis, which is a neurologic disorder that causes variable motor, sensory, visual, and cerebellar dysfunction as a result of multiple focal areas of CNS demyelination. The patient’s orbital pain is likely due to optic neuritis. Dyschromatopsia is the change in color perception and may be more prominent than visual disturbance. Although MRI is the gold standard, lumbar puncture can aid in the diagnosis. The lumbar puncture in approximately 50% of the cases will show pleocytosis, which is an increased number of lymphocytes. In 85%–95% of cases, there will be oligoclonal bands of immunoglobulin G.

IgM and IgG antibodies to B. burgdorferi (A) is seen in the CSF in patients with secondary Lyme disease. A positive CSF VDRL (C) is seen in patients with tertiary syphilis. Xanthochromia (D) is a yellow discoloration of the CSF sometimes seen in patients with a subarachnoid hemorrhage.

Multiple Sclerosis
• Patient will be a caucasian female
• Complaining of pain with eye movement, monocular vision loss, sensory abnormalities
• PE will show spinal electric shock sensation with neck flexion (Lhermitte phenomenon)
• CSF will show ↑ IgG protein, WBC pleocytosis
• Diagnosis is made by T2-weighted MRI
• Most commonly caused by a demyelinating disorder
• Treatment is symptomatic, methylprednisolone
• Comments: Bilateral internuclear ophthalmoplegia (eyes can’t look at nose) is pathognomonic

There are 7 types of botulinum toxin (A through G) produced by C. botulinum, but only types A, B, E, and F cause illness in humans. Clinically, patients first exhibit cranial nerve dysfunction, with diplopia, dysphonia, dysphagia, and dysarthria being most prominent. Vertigo is also a common symptom. Subsequently, a descending symmetrical weakness occurs, involving the upper and lower extremities and the muscles of respiration. Decreased salivation (due to blockade of cholinergic fibers) causes a dry mouth, which may be so severe that patients complain of a painful tongue and sore throat. This constellation of symptoms should prompt the emergency physician to inquire about the ingestion of home-canned foods.

Diphtheria (B) is associated with descending paralysis. It is distinguished by the prolonged interval between pharyngitis and neurologic symptoms. Eaton-Lambert syndrome (C) is a rare autoimmune disease associated with descending paralysis but usually does not involve bulbar muscles. More than half of patients with Eaton-Lambert syndrome have an underlying malignancy, most commonly small cell lung cancer; it is therefore regarded as a paraneoplastic syndrome. Myasthenia gravis (D) is an autoimmune disease associated with antibodies that block acetylcholine receptors at the postsynaptic junction. The hallmark of myasthenia gravis is fatigability. Muscles become progressively weaker during periods of activity and improve after periods of rest. Muscles that control eye and eyelid movement, facial expressions, chewing, talking, and swallowing are especially susceptible. However, no autonomic symptoms are present.

The patient’s exam is consistent with optic neuritis, an acute monocular loss of vision caused by focal demyelination of the optic nerve. Most cases are retrobulbar and do not involve any visible changes on fundoscopy (especially during an acute episode). But, on occasion and with more protracted cases, optic disk pallor may be seen. An afferent pupillary defect, however, is always present. Approximately 30% of patients presenting with acute optic neuritis develop multiple sclerosis within 5 years. The classic clinical syndrome of MS consists of recurring episodes of neurologic symptoms that rapidly evolve over days and slowly resolve.

Controlling blood glucose levels (A) has not been shown to influence the course of optic neuritis or multiple sclerosis. Optic neuritis is not associated with (B) increased (i.e., > 20) intraocular pressure. Magnetic resonance venography (MRV) (C) does not have a role in the diagnosis of optic neuritis or MS. However, a T₂-weighted MRI can aid in the diagnosis by demonstrating lesions in the periventricular white matter—a finding that differentiates simple optic neuritis (where white matter changes are absent) from MS. Such an approach is critical in restoring vision in cases of central retinal artery occlusion (E), not optic neuritis.

The patient is most likely suffering from Guillain-Barré syndrome, a progressive, ascending demyelinating polyneuropathy that typically begins with lower extremity weakness. Classically, GBS presents with symmetric lower extremity weakness, decreased or absent deep tendon reflexes, and little or no sensory involvement (although variable). It follows a respiratory or gastrointestinal infection by weeks to days. Common organisms implicated include Campylobacter jejuni, cytomegalovirus, Epstein-Barr virus, and Mycoplasma pneumoniae. Elevated protein with only a mild pleocytosis on cerebrospinal fluid analysis (termed albuminocytologic dissociation) is highly specific in the clinical setting of suspected GBS. Patients with probable GBS should receive a neurology consult and be admitted for either intravenous immunoglobulin (IVIG) therapy or plasma exchange. Both IVIG and plasma exchange have been demonstrated to be more effective than placebo has, but no advantage is incurred upon administration of both therapies. Neither therapy has been proven more effective than the other.

Selective enhancement of the anterior spinal nerve roots (D) on MRI is suggestive. Nearly 33% of patients diagnosed with GBS will require ventilator support. Factors associated with an increased need for ventilator support include a decreased forced vital capacity (FVC) (C) and a negative inspiratory force (NIF) less than 30 cm water. Other useful adjuncts include peak expiratory flow rate (PEFR) and arterial blood gas to evaluate for carbon dioxide retention. Corticosteroids alone (B) are no longer recommended, but IV steroids coadministered with IVIG may speed recovery. Regardless, steroids have no role in the diagnosis of GBS.

This patient is having a myasthenic crisis, caused by antibodies to the acetylcholine receptor (AChR) at the neuromuscular junction. Failure to respond to acetylcholine stimulation leads to decreased muscle fiber activationand muscle weakness. The antibodies cause AChR degradation, dysfunction, and blockade. Ptosis and diplopia are most commonly the first symptoms. Patients may also experience dysphagia, proximal muscle weakness, and dyspnea. A full myasthenic crisis may lead to respiratory failure due to flaccid paralysis of the muscles of respiration.

Botulinum toxin inhibits acetylcholine release at the synapse (B). It is produced by Clostridium botulinum, an anaerobic spore-forming bacterium. C. botulinum occurs naturally in the soil and causes human disease when ingested. Botulism is associated with a descending symmetric paralysis. Amyotrophic lateral sclerosis (ALS) is caused by a mutation of superoxide dismutase (C) leading to an abnormal response to stress and cell death. Central and peripheral nerves are affected with sparing of sensory and cognitive function. Initial symptoms are muscle weakness, atrophy, fasciculations, dysarthria, and dysphagia. Parkinson’s disease is associated with depigmentation and dopaminergic neuron loss (D) in the midbrain, especially the substantia nigra. It is also characterized by Lewy bodies, which are cytoplasmic inclusions seen under the microscope. Parkinson’s disease is characterized by tremor, cogwheel rigidity, bradykinesia or akinesia, and postural and equilibrium impairment.

Normal pressure hydrocephalus (NPH) is characterized by the following characteristics: wet, wacky, and wobbly. More specifically, it includes a triad of progressive dementia, ataxia and urinary frequency or incontinence. It is a reversible cause of dementia and results from defective uptake of CSF. Head CT will reveal ventricular enlargement. Atrophy may occur in chronic alcoholics or the elderly, but is neither sensitive nor specific for NPH. A brain mass can cause a variety of symptoms, but headache with a neurologic deficit would be a more common presentation

The presence of myopathy and cerebellar degeneration helps distinguish alcoholic neuropathy. Otherwise, the clinical pictures are similar. Incontinence is not a typical feature of either.

Though evidence supporting IV immune globulin is weak, it is an accepted alternative to plasmapheresis. Pyridostigmine and neostigmine are used orally for maintenance and not for acute crisis, and the IV dose might cause complications from the cholinergic excess such as increased secretions.