Cereda, C.

Granziera, C.

Kuntzer, T.

Vingerhoets, F.

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J Neurol (2008) 255:1423–1424DOI 10.1007/s00415-008-0930-7 LETTER TO THE EDITORSJON 2930 encountered in the anterior inter-osseous syndrome.In January 2007, a 67-year-old female with hypertension and  hypercholesterolemia, presented with a sudden onset of an isolated left hand paresis. Detailed exami-nation revealed severe paresis of thumb and index flexion (thumb-index pinch deficit) and light  paresis of the flexion of the other  fingers and interosseous muscles (M5-). Pronatus quadratus muscle function, tested with a flexed elbow, as well as fingers extensors’ were spared. Deep tendon reflexes were symmetric. No other neurological symptoms were observed. Acute perfusion cranial CT scan did not visualize any cerebral lesion. Brain MRI performed after 8 days re-vealed a hyperintense signal in T2 and a point-shaped Gadolinium enhancement in T1 WI localized in the “hand-knob” [2, 5] (Fig. 1).  Vascular investigations were  negative and transthoracic echo-cardiography showed a moderately patent foramen ovale; procoagulant factors were negative. Electromyog-raphy was planned but not per-Cristina GranzieraT. KuntzerF. VingerhoetsC. CeredaSmall cortical stroke in the “hand knob” mimics anterior interosseous  syndromeReceived: 6 October 2007Received in revised form: 2 February 2008Accepted: 6 March 2008Published online: 25 September 2008Sirs: Monoparesis caused by cere-bral insult is rare and is usually caused by mass lesions rather than by vascular damage [1, 7]. At the beginning of the 20th century, J. Lhermitte reported that small cor-tical strokes could cause weakness restricted to a particular group of fingers (“pseudoperipheral palsy”) [6]; recent imaging studies showed that these symptoms are due to motor hand area (“hand knob”)  lesions [4, 5, 9, 13] and affect pre-dominantly muscles supplied by the “ulnar” or the “radial” nerve [4, 12]. To date, no reports are avail-able about strokes leading to pare-sis of the muscles exclusively con-trolled by the median nerve. We describe a patient with a point-lesion in the right “hand knob”, who presented with a pre-dominant deficit of the left thumb-index pinch, a weakness usually formed after visualizing the lesion in brain MRI. Clinically, the patient recovered almost completely within 7 days. This patient presented with an acute hand palsy affecting predom-inantly two forearm muscles, the flexor pollicis longus and the flexor digitorum profundus of the 2nd finger, which control the thumb- index pinch movement. These two muscles are supplied by the ante-rior interosseous nerve (AIN), which is a pure motor branch of the median nerve. Peripheral nerve lesions involving the AIN are asso-ciated with brachial neuritis, trauma and extrinsic compression [11]. In our patient, the hypothesis of a vascular central nervous sys-tem etiology was supported by the acute instauration of the symp-toms, the presence of a very mild diffuse paresis in other muscles of the hand and the presence of  multiple cerebrovascular risk  factors. A small cortical stroke was confirmed by a brain MRI and an embolic etiology was considered, based on the location of the lesion and on the presence of a patent Dr. C. Granziera, MD, PhD () · T. Kuntzer, MD · F. Vingerhoets, MD · C. Cereda, MDService de NeurologieCHUV BH 191011 Lausanne, SwitzerlandTel.: +41-21/314-1184Fax: +41-21/314-1256E-Mail: Cristina.Granziera@hospvd.chThis manuscript has not been submitted for publication elsewhere and will not be sub-mitted elsewhere while under consideration for this journal.Fig. 1  a MRI, T2WI. Horizontal slice showing a point-shaped hyperintense lesion in the omega-shaped “hand knob” area. b MRI, T1WI (gadolinium): Horizontal slice showing a point-shaped contrast enhancement cor-responding to the T2 hyperintensity1424 foramen ovale. The lesion was  localized in a region of the hand-knob, which has been described to control the muscles innervated by the radial nerve [3, 4], though the location of ulnar and radial repre-sentation shows some degree of flexibility within the knob. It is actually debated whether the predominance of weakness in a certain muscle group (ulnar, radial, median) is due to lesions of areas controlling selected muscles move-ments [4] or could be not spatially segregated [10]. This case report supports the theory that the motor representation in the hand area does not follow the classical topog-raphy in the human motor hand area. Future fMRI [8], transcranial magnetic stimulation [8] and fiber tracking studies should be per-formed to better elucidate this point. ■ Conflict of interest  The authors declare no conflict of interest.References 1. Ashizawa T, Rolak LA, Hines M (1986) Spastic pure motor monoparesis. Ann Neurol 20:638–641 2. Boroojerdi B, Foltys H, Krings T, Spetzger U, Thron A, Topper R (1999) Localization of the motor hand area using transcranial magnetic stimula-tion and functional magnetic reso-nance imaging. Clin Neurophysiol 110:699–704 3. Gass A, Szabo K, Behrens S, Rossma-nith C, Hennerici M (2001) A diffu-sion-weighted MRI study of acute ischemic distal arm paresis. Neurology 57:1589–1594 4. Kim JS (2001) Predominant involve-ment of a particular group of fingers due to small, cortical infarction. Neu-rology 56:1677–1682 5. Lee PH, Han SW, Heo JH (1998) Iso-lated weakness of the fingers in corti-cal infarction. Neurology 50:823–824 6. Lhermitte (1909) De la valeur sémiolo-gique des troubles de la sensibilité à disposition radiculaire dans les lésions de l’encéphale. Sem Méd 24:277 7. Paciaroni M, Caso V, Milia P, Venti M, Silvestrelli G, Palmerini F, Nardi K,  Micheli S, Agnelli G (2005) Isolated monoparesis following stroke. J Neurol Neurosurg Psychiatry 76:805–807 8. Park MC, Goldman MA, Park MJ, Friehs GM (2007) Neuroanatomical  localization of the ‘precentral knob’ with computed tomography imaging. Stereotact Funct Neurosurg 85:158–161 9. Phan TG, Evans BA, Huston J (2000) Pseudoulnar palsy from a small infarct of the precentral knob. Neurology 54:218510. Schieber MH (2001) Constraints on  somatotopic organization in the  primary motor cortex. J Neurophysiol 86:2125–214311. Stewart J (1987) Focal peripheral  neuropathies. New York: Raven12. Takahashi N, Kawamura M, Araki S (2002) Isolated hand palsy due to  cortical infarction: localization of the motor hand area. Neurology 58:1412–141413. Yousry TA, Schmid UD, Alkadhi H, Schmidt D, Peraud A, Buettner A,  Winkler P (1997) Localization of the motor hand area to a knob on the pre-central gyrus. A new landmark. Brain 120(Pt 1):141–157

Small cortical stroke in the "hand knob" mimics anterior interosseous syndrome

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Small cortical stroke in the "hand knob" mimics anterior interosseous syndrome

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