Anomalous innervations by;Chaman Lal
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Anomalous innervations by;Chaman Lal

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Anamalous innervations EMG& NCS findings and recognition.

Anamalous innervations EMG& NCS findings and recognition.

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Anomalous innervations by;Chaman Lal Anomalous innervations by;Chaman Lal Presentation Transcript

  • ANOMALOUS INNERVATIONS Chaman Lal Karotia (CK) B.S.PT(KU); MPPS(Pak);PG (Clinical NeurophysiolgyTechnology),(AKUH); Member of AANEM; Member of ASET; Aga Khan University Hospital , Karachi.
  • What is anomaly? a·nom·a·ly (-nm-l) n:Gk, anomalos, irregular A deviation from what is regarded as normal or norm Or Marked deviation from normal, especially as a result of congenital or hereditary defects. anomalous, adj15-X-12 Anomalous Innervations By:CK 3
  • Why is Important to know? If these conditions remain unrecognized, they can be mistakenly interpreted as pathological conditions or technical faults.15-X-12 Anomalous Innervations By:CK 4
  • A-Upper limb anomalous innervations Martin – Gruber Anastomosis (Median to Ulnar anastomosis) All Ulnar- hand innervations Ulnar to median anastomosis Superficial Radial nerve innervations on dorsum of the hand15-X-12 Anomalous Innervations By:CK 5
  • B-Lower limb anomalous innervations Accessory Peroneal nerve Tibial to Peroneal anastomosis15-X-12 Anomalous Innervations By:CK 6
  • Martin- Gruber anastomosis It is most common anomalous innervation in upper limb. Present in 15 – 30 % of patients. It is manifested by cross over of median-to- ulnar fibres. Cross over commonly occurs in mid forearm either from the main median trunk or from one of its branches (most commonly anterior interossius nerve). It may present unilaterally or bilaterally. It involves only motor fibres.15-X-12 Anomalous Innervations By:CK 7
  • Pathway and Innervation! After cross over in the mid forearm, median fibres run with the distal ulnar nerve to innervate via any of the following means:1. Innervation to hypothenar muscles(abductor digiti minimi).2. Innervation to FDI muscle.3. Innervation to the ulnar innervated thenar muscles.4. Combination of these.15-X-12 8 Anomalous Innervations By:CK
  • When is it recognized ? During routine ulnar conduction studies. During ulnar conduction studies when recorded from FDI. During routine median studies. When co- existent CTS study is performed.15-X-12 Anomalous Innervations By:CK 9
  • Recording During Routine Ulnar Studies If anastomotic fibres innervate abductor digiti minimi, > 10 % drop in CMAP amplitude is noted between wrist and below elbow stimulation sites.( Higher amplitudes are seen with distal stimulation). Median nerve stimulation should be performed at the wrist and at the antecubital fossa (AF) while recording the hypothenar muscles.15-X-12 Anomalous Innervations By:CK 10
  • NCS recording from ADQ muscle15-X-12 Anomalous Innervations By:CK 11
  • Cont’d… The differential diagnosis of this pattern (i.e., higher amplitude distally than proximally) includes the following: 1) Excessive stimulation of the ulnar nerve at the wrist resulting in co-stimulation of the median nerve, 2) Submaximal stimulation of the ulnar nerve at the below-elbow site, 3) Conduction block of the ulnar nerve between the wrist and below-elbow sites, or 4) An MGA with crossing fibers innervating the hypothenar muscles.15-X-12 Anomalous Innervations By:CK 12
  • Cont’d… If no MGA is present, a small positive deflection usually is recorded with both the wrist and antecubital fossa stimulation sites, reflecting a volume conducted potential from median muscles. If an MGA is present, a small positive volume-conducted potential will be present with median nerve stimulation at the wrist; however, median stimulation at the antecubital fossa will evoke a small CMAP over the abductor digiti minimi.15-X-12 Anomalous Innervations By:CK 13
  • Cont’d… The amplitude of the CMAP evoked by stimulating the median nerve at the ante- cubital fossa (recording the hypothenar muscles) will approximately equal the difference between the CMAP amplitudes evoked with ulnar nerve stimulation at the wrist and below-elbow sites (recording the hypothenar muscles). If its not identified it may give a false impression of technical fault or conduction block.15-X-12 Anomalous Innervations By:CK 14
  • NCS recoding from ADQ15-X-12 Anomalous Innervations By:CK 15
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  • Cross over of median to ulnar fibres supplying FDI If anastomotic fibres innervate FDI, >10 % of amplitude drop occurs between stimulation at the wrist and below-elbow site. Higher amplitude being found by distal stimulation. It may give a false impression of technical mistake or conduction block. Question:- When NCS from FDI is done? 15-X-12 Anomalous Innervations By:CK 17
  • How to confirm for MGA ? After ruling out the technical faults, median nerve is stimulated at wrist and at anticubital fossa while recording from FDI. Higher amplitude CMAP is recorded with proximal stimulation than with wrist stimulation in case of MGA. The difference between wrist and anticubital fossa stimulations approximates the drop in amplitude between proximal and distal stimulation sites when stimulating ulnar nerve.15-X-12 Anomalous Innervations By:CK 18
  • NCS recording from FDI muscle15-X-12 Anomalous Innervations By:CK 19
  • Cross over of median-to-ulnar fibres innervating any of the ulnar innervated thenar muscles. Adductor pollicis and deep head of flexor pollicis brevis are ulnar nerve innervated thenar muscles. When these muscles are innervated by MGA, median motor studies show a characteristic pattern of higher CMAP amplitudes with proximal median stimulation than distal stimulation.15-X-12 Anomalous Innervations By:CK 20
  • NCS recording from APB muscle15-X-12 Anomalous Innervations By:CK 21
  • 15-X-12 Anomalous Innervations By:CK 22
  • How to confirm for MGA ? After ruling out the technical faults, ulnar nerve is stimulated at the wrist and below elbow sites while recording from thenar muscles. Normally it results in a CMAP (due to ulnar innervated muscles in thenar eminence) of almost same amplitude, with proximal as well as distal stimulation. If an MGA is present, CMAP amplitude is lower with proximal stimulation.15-X-12 Anomalous Innervations By:CK 23
  • MGA with co existent CTS As both of these conditions are common, so they might be seen existing together. Co existence of both the conditions should be suspected when proximal median nerve stimulation gives a more positive deflection at the thenar eminence along with fast conduction velocity. In some cases of severe CTS, proximal latency may be shorter than the distal latency.15-X-12 Anomalous Innervations By:CK 24
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  • 15-X-12 26 Anomalous Innervations By:CK
  • Needle EMG in case of MGS In this situation, unexpected results may be seen creating confusion in interpretation. For example, In cases of median nerve dysfunction at the anticubital site, EMG may show abnormal findings in ulnar innervated muscles. In cases of ulnar neuropathy, some of the ulnar innervated muscles may be spared on EMG examination.15-X-12 Anomalous Innervations By:CK 27
  • All Ulnar- hand innervations Among them are cases of the all-ulnar hand. In rare individuals, all or most of the intrinsic hand musculature is innervated by the ulnar nerve. In these individuals, an ulnar nerve lesion at the elbow may cause much more dysfunction in the hand than one typically expects to see.15-X-12 Anomalous Innervations By:CK 28
  • Anomalous innervation between Superficial Radial and the Dorsal Ulnar Cutaneous sensory nervesIn the upper extremity, an anomalousinnervation between the superficial radial andthe dorsal ulnar cutaneous sensory nerves hasbeen described. Normally, sensation to thedorsum of the hand is mediated by bothnerves: the little and ring fingers and medialhand by the dorsal ulnar cutaneous nerve, andthe remainder by the superficial radial nerve. Inrare individuals, the superficial radial nerveinnervates the entire territory.15-X-12 Anomalous Innervations By:CK 29
  • NCS recording in Sup.Radial v/s DUC During nerve conductions, this situation may present as an apparently absent response recording the dorsal ulnar cutaneous sensory nerve. The anomaly can be demonstrated by stimulating the superficial radial nerve in the lateral forearm, with recording electrodes placed over the dorsal ulnar cutaneous nerve territory.15-X-12 Anomalous Innervations By:CK 30
  • 15-X-12 Anomalous Innervations By:CK 31
  • Accessory Peroneal Nerve (APN) The most common anomalous innervation in the lower extremity is the accessory peroneal nerve (APN) in the lateral calf. Patients with an APN have an anomalous innervation to the EDB; the medial portion of the EDB is supplied by the deep peroneal nerve as usual, but the lateral portion is supplied by an anomalous motor branch originating from the superficial peroneal nerve, the APN.15-X-12 Anomalous Innervations By:CK 32
  • 15-X-12 Anomalous Innervations By:CK 33
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  • Tibial to Peroneal anastomosis In addition, there are rare isolated case reports of tibial-to-peroneal and ulnar-to- median anastomosis. If an unusual or unexpected nerve conduction pattern is seen, one should always consider not only technical factors but also the possibility of an anomalous innervation.15-X-12 Anomalous Innervations By:CK 35
  • Question:- All of the following can cause a“positive dip” on routine NCS EXCEPT? A. Co-stimulation. B. Improper recording electrode placement. C. MGA. D. MGA with CTS. E. Submaximal stimulation.15-X-12 Anomalous Innervations By:CK 36
  • Answer:- C Explanation:- When recording over the thenar eminence and stimulating the median nerve at the elbow, a positive dip is not usually seen unless there is concomitant CTS slowing down the action potentials as they enter the hand.15-X-12 Anomalous Innervations By:CK 37
  • Question:- In the MGA: A. Some muscles in the thenar eminence that are typically innervated by the median nerve are innervated by the ulnar nerve. B. The proximal median amplitude is always higher than the distal median amplitude. C. A pseudo-conduction block of the ulnar nerve in the forearm may occur.15-X-12 Anomalous Innervations By:CK 38
  • Cont’d. . . D. The sensory potential recording from digit two has contributions from the median and ulnar nerves. E. Individuals who have this variant may have relative protection from median neuropathy at the wrist.15-X-12 Anomalous Innervations By:CK 39
  • Answer:- C Explanation:- An MGA involving the ADQ would be expected to produce a drop in amplitude when comparing the distal site with the proximal site. This will have an appearance of conduction block in the forearm and not across the elbow.15-X-12 Anomalous Innervations By:CK 40
  • 15-X-12 Anomalous Innervations By:CK 41