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Clinical Reasoning RESIDENT & FELLOW SECTION Clinical Reasoning: Section Editor A 23-year-old woman with paresthesias Mitchell S.V. Elkind, MD, MS and weakness Chafic Karam, MD SECTION 1 peated bone marrow biopsies showed no blasts. No Azita Khorsandi, MD A 23-year-old woman presented with a 6-month his- intrathecal chemotherapy was given. The appendici- Daniel J. MacGowan, tory of progressive left hand weakness associated with tis was treated for 1 month with moxifloxacin prior MD left ulnar distribution numbness and paresthesias. At to an elective appendectomy. the onset of these symptoms, she recalled shooting Bone marrow examination and peripheral blood pain up and down the medial left forearm. She de- smear were normal at the time of neurologic Address correspondence and nied any neck pain. presentation. reprint requests to Dr. Chafic The patient had been diagnosed with acute my- Questions for consideration: Karam, 353 East 17th Street, eloid leukemia (AML) type 5a and appendicitis 9 #22D, New York, NY 10003 [email protected] months previously. At that time lumbar puncture 1. Where can the lesion be localized and what could and brain and spine MRI were negative for CNS be its nature in the context of this patient’s involvement. A right Hickman catheter was placed. history? She was treated with cytarabine and idarubicin and 2. How could the differential diagnosis be narrowed was thought to be in complete remission after re- further? GO TO SECTION 2 From the Departments of Neurology (C.K., D.J.M.) and Neuro-radiology (A.K.), Beth Israel Medical Center, Albert Einstein College of Medicine, New York, NY. Disclosure: The authors report no disclosures. Copyright © 2009 by AAN Enterprises, Inc. e5 SECTION 2 In this patient, the neurologic examination The evaluation of a patient with hand weakness, showed 4/5 strength of the left interossei, flexor carpi numbness, and paraesthesias would start with localiz- ulnaris, ulnar flexor digitorum profundus, and ad- ing the lesion. A lesion in the CNS, involving the ductor pollicis. There was no other weakness. There contralateral precentral gyrus and anterior aspect of was reduced pin sensation in the medial aspect of the 1 the postcentral gyrus, is highly unlikely, especially 4th digit, entire 5th digit, hypothenar eminence, and with the shooting pain up and down the medial left medial one third of the dorsal hand. Tinel sign was forearm. positive in the left ulnar cubital tunnel. Sensation of In the peripheral nervous system, radiculopathy, the left medial forearm was intact. Tone, reflexes, plexopathy, or a nerve lesion could be responsible for vibration, coordination, and gait were normal. There combined motor and sensory impairment in the was no Horner syndrome. hand. Minor repetitive trauma can cause nerve dam- The neurologic examination indicates that the le- age, resulting in carpal tunnel syndrome or ulnar sion is localized to the peripheral nervous system. neuropathy at the elbow. The radial, ulnar, or me- The symptoms can be explained by left ulnar neu- dian nerve could have been damaged during the pa- tient’s recent surgery. Other causes of isolated ropathy, left C8 radiculopathy, or a lower trunk/ neuropathy in this patient include a mononeuritis medial cord plexopathy. The absence of neck pain multiplex caused by blast cell infiltration of the left argues against a nerve root lesion. ulnar nerve. The brachial plexus may also be com- Questions for consideration: pressed or infiltrated by an extramedullary myeloid tumor (EMT) in the setting of leukemia. Neurotox- 1. What are the clinical findings in an ulnar neurop- icity secondary to the chemotherapy is more likely to athy and a lower trunk/medial cord plexopathy? be bilateral, symmetric, and ascending. 2. What is the role of an EMG/NCS study? GO TO SECTION 3 e6 Neurology 72 January 13, 2009 SECTION 3 and assess for weakness of C8/T1 non-ulnar inner- Patients with ulnar neuropathy usually present with vated muscles such as flexor pollicis longus, extensor numbness and paresthesias involving the 5th finger indicis proprius, opponens and abductor pollicis and the ulnar half of the 4th digit. Some patients brevis. may notice a dull ache down the ulnar border of the This patient had sensory symptoms of an ulnar forearm. The symptoms can be elicited by having the neuropathy at the elbow, with a positive Tinel sign, patient flex the elbow or by tapping over the ulnar which is suggestive of UNE. However, the shooting nerve at the cubital tunnel (Tinel sign). C8 radicu- pain up and down her medial forearm is atypical. lopathy causes pain and numbness of the 4th and 5th This distribution of pain fits a C8 and T1 radiculop- digits. T1 root pain causes pain in the shoulder joint athy or a lower trunk/medial cord plexopathy. The radiating down the medial side of the upper arm and motor findings suggest an ulnar pattern of weakness, forearm with numbness of the medial arm and fore- although FCU weakness is atypical. arm. Atrophy and weakness reflect motor axon or EMG/NCS studies could help determine the af- anterior horn cell loss. A proximal ulnar neuropathy fected muscles and sensory nerve deficits, thus indi- at the elbow (UNE) results in weakness in the in- cating if her symptoms are secondary to UNE terosseous muscles, adductor pollicis, and long flex- secondary to minor elbow trauma or positioning at ors of the 4th and 5th digits. Usually it spares the the time of her surgery vs a lower trunk/medial cord 2 flexor carpi ulnaris (FCU). A T1 root lesion will brachial plexopathy. In 1999, the American Associa- preferentially involve the abductor pollicis brevis tion of Electrodiagnostic Medicine (AAEM) issued a (APB) and opponens. A C8 root lesion will cause Practice Parameter for Electrodiagnostic Studies in weakness in the flexor carpi ulnaris, deep finger flex- Ulnar Neuropathy at the Elbow. The strongest evi- ors, flexor pollicis longus, interossei, adductor polli- dence of ulnar neuropathy at the elbow includes an cis, and extensor indicis proprius muscles. Medial absolute motor nerve conduction velocity (NCV) cord brachial plexopathy would result in weakness of from above elbow (AE) to below elbow (BE) of less the muscles innervated by the ulnar nerve in addition than 50 m/s and an AE-to-BE segment greater than to the median-innervated intrinsic hand muscles, i.e., 10 m/s slower than BE-to-wrist (W) segment. Other opponens and APB. Thus in order to differentiate findings include a decrease in compound muscle ac- UNE from C8/T1 radiculopathy and lower trunk/ tion potential (CMAP) negative peak amplitude medial cord brachial plexopathy, one would search from BE to AE greater than 20% suggesting a con- for sensory loss extending into the medial forearm duction block or temporal dispersion indicative of focal demyelination and a significant change in Table Motor and nerve conduction studies of the ulnar nerve CMAP configuration at the AE site compared to the BE site. Ulnar sensory responses should be recorded Conduction Latency, ms Amplitude, mV velocity, m/s from the fifth fingers and dorsal ulnar palm. In this patient, the left ulnar distal motor response Motor nerve conduction studies latency was prolonged. There was diffuse left ulnar L ulnar/ADM forearm and across elbow slowing with reduced left Wrist 4.55 3.8 ulnar motor response amplitudes. The ulnar F-waves Below the elbow 9.3 3.2 42.1 done with supramaximal stimulation at the wrist Above the elbow 11.7 1 41.7 were prolonged. There was no conduction block, fo- L ulnar/FDI cal area of slowing, or temporal dispersion. The left Wrist 4.4 4.2 ulnar and dorsal digital ulnar cutaneous sensory re- Below the elbow 8.85 2.7 44.9 sponse amplitudes were very reduced. The bilateral Above the elbow 11.95 2.1 32.3 medial cutaneous nerve of forearm sensory responses Sensory nerve conduction studies were normal. Median motor and sensory conduction R ulnar-V-antidromic 2.7 70.3 50 studies and F-waves were normal. Needle EMG of muscles in the left upper extrem- L ulnar-V-antidromic 4.45 4.9 27 ity showed spontaneous fibrillations and positive R ulnar-dorsal-antidromic 1.45 14.4 55.2 sharp waves with reduced recruitment of prolonged L ulnar-dorsal-antidromic 2.3 3.7 37 and polyphasic motor units in all left ulnar inner- The moderately prolonged left distal ulnar motor response latency and conduction velocity vated muscles including the FCU. All other muscles slowing in the forearm and across the elbow reflects a loss of left ulnar large fiber axons. were normal, including APB, flexor pollicis longus, There is no evidence of selective slowing in the left ulnar nerve across the elbow. These and extensor indicis proprius (table). findings were felt to be consistent with a proximal, axonal left ulnar neuropathy rather than a lower trunk plexopathy since the medial antebrachial cutaneous sensory, median motor The findings are consistent with subacute, proxi- conduction studies, and needle EMG of the abductor pollicis brevis were normal. mal, and axonal left ulnar neuropathy. The pro- Neurology 72 January 13, 2009 e7 longed ulnar F-waves were thought to be due to large IV/V 4/5, interossei and adductor pollicis 2/5; and fiber axon loss in the ulnar nerve. on the right: extensor hallucis longus (EHL) 2/5 and The normal left medial antebrachial cutaneous extensor digitorum brevis (EDB) 4/5. All other mus- sensory response and needle EMG of the abductor cles were normal. Pin sensation was reduced in the left pollicis brevis favors isolated ulnar neuropathy. hypothenar eminence, 5th and medial 4th digits, and However, the involvement of the flexor carpi ulnaris medial forearm.
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