A Woman with Progressive Ataxia and Hemiparesis on the Right Side
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Practice Teaching Case Report right side, and brain MRI revealed a 5 × 5.4 × 6 cm extra-axial mass in the A woman with progressive ataxia and hemiparesis on the right posterior fossa. The mass was isointense on T1-weighted imaging right side: Where’s the lesion? (Figure 2A) and isointense to hy- pointense on T2-weighted imaging The case: A 53-year-old right-handed cally be caused by a contrecoup lesion or (Figure 2C), with homogeneous con- woman reported 2 years of gait difficul- contusion but may also be attributed, if trast enhancement suggestive of ties and progressive clumsiness and only rarely, to Kernohan’s notch phe- meningioma (Figure 2B and Figure 2D). weakness of her right upper and lower nomenon.2 In 1929, Kernohan and Wolt- The mass was associated with significant extremities. She was referred to our neu- man described hemiparesis in a patient mass effect on the adjacent right cerebel- rology service for assessment and was with an ipsilateral supratentorial mass le- lar hemisphere and pons, with compres- found to have abnormal speech (spastic sion,2 which resulted in displacement of sion of the fourth ventricle and dilatation dysarthria) and horizontal nystagmus on the brain stem against the incisura of the of the lateral and third ventricles, consis- leftward gaze, with fast component to tentorium cerebelli. The groove in the pe- tent with noncommunicating hydro- the right. The left side of her body was duncle caused by this displacement came cephalus. The meningioma caused normal, but she had right-side hyperto- to be called Kernohan’s notch. The false- downward cerebellar tonsillar herniation nia, hyperreflexia and mild hemiparesis localizing ipsilateral hemiparesis, result- and leftward and upward transtentorial with extensor plantar response. She also ing from compression of the crus cerebri herniation of the brain stem (Figure 2C had dorsiflexion and eversion of the by the tentorium, likewise became and Figure 2D), which resulted in right right ankle. She exhibited past-pointing known as the Kernohan–Woltman syn- hemiparesis because of compression of on the right upper limb and had a posi- drome or Kernohan’s notch phenome- the left cerebral peduncle by the tento- tive result on heel-to-shin testing of the non (Figure 1A). Although originally de- rium cerebelli (Figure 1B). A ventricu- right lower limb. Sensation was intact, scribed in a patient with a primary brain loperitoneal shunt was inserted, after and other results of the neurologic and tumour, the phenomenon may also occur which the meningioma was partially ex- general physical examinations were un- with traumatic brain injury or with dis- cised to preserve function of the adher- remarkable. What is the differential di- placement of the cerebral peduncles. ent lower cranial nerves. The patient sub- agnosis of this case of hemiparesis and The patient described here pre- sequently underwent gamma knife incoordination on the right side? sented with ataxia and weakness on the irradiation of the remnant tumour. Post- Motor loss arising from the brain or the brain stem usually results from a lesion on the contralateral side.1 The corti- cospinal axons descend from the motor cortex and pass through the internal capsule and crus and then through the brain stem with the corticobulbar tract. Most (80%–90%) of the corticospinal fibres decussate to the opposite side at the medullary pyramids, continuing their descent in the spinal cord as the lateral corticospinal tract. The remain- ing fibres descend uncrossed as the an- terior corticospinal tract.1 Coordination of movement is mediated by the cere- Figure 1: (A) Schematic coronal section of the brain showing large (supratentorial) right bellum, which processes signals from subdural hematoma causing ipsilateral transtentorial herniation, which has resulted in the motor cortex to the ipsilateral compression of the contralateral cerebral peduncle (broken, red arrow). This led to ipsilat- spinal cord (and thence to the muscles) eral (right-sided) weakness. (B) Schematic coronal section of the brain showing (infraten- via the spinocerebellar tracts. Thus, torial) right meningioma (M) causing upward and leftward displacement of the midbrain and cerebral peduncles, which has resulted in compression of the left cerebral peduncle ataxia is usually caused by a lesion in and corticospinal tracts against the tentorium cerebelli (open arrow), which contributed to the cerebellar hemisphere or the spi- 1 the ipsilateral (right-side) weakness. In both figures, the solid arrows indicate the direction nocerebellar tracts on the same side. of shift due to the mass effect, either from the subdural hematoma or from the tumour. DOI:10.1503/cmaj.070337 Ipsilateral weakness may paradoxi- CMAJ • July 31, 2007 • 177(3) 247 © 2007 Canadian Medical Association or its licensors Practice operative recovery was uneventful, and nar stroke in the pons or internal cap- cysticercosis, can mimic ataxic hemi- the patient recovered normal function. sule. Weakness in ataxic hemiparesis is paresis by involving the contralateral The patient’s ipsilateral weakness re- caused by disruption of the corticospinal corticospinal tract and the ipsilateral sulted from an infratentorial, rather tracts, and the ataxia is attributed either cerebellum or spinocerebellar tracts. than a supratentorial, mass. The large to involvement of the frontopontocere- Meningiomas are the second most cerebellar meningioma pushed upward bellar connections or to impaired posi- common brain tumour in adults.5 Most and to the left, causing the midbrain and tion sense.4 A lesion localized to the are benign, but up to 20% exhibit clini- left cerebral peduncle to be compressed cerebellar hemisphere should cause ip- cally aggressive features. The annual in- by the tentorium cerebelli. Kanis and as- silateral ataxia, but not weakness, unless cidence of meningiomas is estimated at sociates3 described a similar phenome- there is concomitant disruption of the between 0.8 and 4.9 per 100 000, but the non in a patient with an inferior cerebel- corticospinal tracts. In this patient, the true incidence is probably higher, as lar infarction; that patient experienced displacement of the brain stem and many benign meningiomas are asymp- ipsilateral hemiparesis because of cere- cerebral peduncle to the left caused tomatic.5 Intracranial meningiomas are bellar edema, which caused displace- weakness on the right side by compress- usually surgically excised, although ra- ment of the medulla with impaction of ing the contralateral corticospinal fibres diosurgery and radiation therapy may be the pyramids upon the clivus. against the tentorium cerebelli, whereas considered for patients whose lesions The combination of right-side weak- the cerebellar meningioma on the right are deemed inoperable, who refuse sur- ness and ataxia in the patient reported side caused ipsilateral ataxia. Other con- gery, who have histologic findings sug- here mimicked ataxic hemiparesis, ditions, such as multiple sclerosis, gestive of an aggressive lesion or who which is usually associated with a lacu- chronic subdural hematoma and neuro- undergo inadequate resection. The pa- tient described here, who underwent surgical resection and then radiosurgery (because of incomplete resection of the tumour), had an uneventful recovery. Jing-Hui Yik Yong Loo Lin School of Medicine National University of Singapore Raymond C.S. Seet MBBS MMed (IntMed) Yong Loo Lin School of Medicine National University of Singapore Division of Neurology National University Hospital Chong-Han Pek Yong Loo Lin School of Medicine National University of Singapore Erle C.H. Lim MBBS MMed (Int Med) Yong Loo Lin School of Medicine National University of Singapore Division of Neurology National University Hospital Singapore This article has been peer reviewed. Competing interests: None declared. REFERENCES 1. Young PA, Young PH. Basic clinical neuroanatomy. Baltimore: Williams and Wilkins; 1997. 2. Kernohan JW, Woltman HW. Incisura of the crus due to contralateral brain tumor. Arch Neurol Psy- chiatry 1929;21:274-87. 3. Kanis KB, Ropper AH, Adelman LS. Homolateral hemiparesis as an early sign of cerebellar mass ef- fect. Neurology 1994;44:2194-7. Figure 2: Sagittal T1-weighted MRI, without (A) and with (B) gadolinium contrast agent. 4. Gorman MJ, Dafer R, Levine SR. Ataxic hemipare- Transverse T2-weighted (C) and coronal T1-weighted (D) images, both with gadolinium con- sis: critical appraisal of a lacunar syndrome. Stroke × × 1998;29:2549-55. trast agent, show 5 5.4 6 cm meningioma. The infratentorial mass is evident in Figure D, 5. McMullen KP, Stieber VW. Meningioma: current pushing the brain stem upward against the tentorium cerebelli at Kernohan’s notch. treatment options and future directions. Curr Treat Options Oncol 2004;5:499-509. 248 CMAJ • July 31, 2007 • 177(3).