170 Neuroanatomy: Draw It to Know It
Medullary Syndromes ( Advanced )
Case I
Patient presents with dizziness, incoordination, double
vision, trouble swallowing, sensory disturbance, and
pupillary asymmetry. Exam reveals left -side cerebellar
ataxia; loss of pain and temperature sensation in the left
face; loss of pain and temperature sensation on the right
side of the body; left -side Horner’s syndrome (ptosis,
anhidrosis, and miosis); dysarthria and impaired gag
refl ex; ocular skew with the left eye lower than the right;
and right-beating nystagmus (slow phase to the left , fast
phase to the right).
Draw the left half of the medulla and defi ne the planes
of the diagram. Th is is an axial, anatomic view of the
medulla with the anterior surface of the brainstem at the
bottom of the page and the posterior surface at the top.
First, show that the left cerebellar ataxia results from
injury to the left inferior cerebellar peduncle. Next, show
that the loss of sensation on the left side of the face results
from spinal trigeminal tract and nucleus involvement.
Th en, show that the loss of pain and temperature sensa-
tion on the right side of the body is from injury to the
anterolateral system bundle (spinothalamic fi bers) on
the left. Note that this case represents the classic pattern
of sensory loss for this injury type but depending on the
rostral-caudal level of the lesion, variation in sensory loss
exists; most notably, the facial sensory loss can occur
contralaterally or bilaterally rather than ipsilaterally (as
shown here).
Now, show that the hoarseness and dysphagia is mostly
from involvement of the left nucleus ambiguus. Next,
show that the left -side Horner’s syndrome is from injury
to descending hypothalamospinal tract fi bers on the left.
Indicate that the descending hypothalamospinal fi bers
are believed to lie ventral to the solitary tract; injury to
the solitary tract, itself, produces taste disturbance.
Next, show that the ocular skew deviation — the left
eye being more inferior that the right, and the right-beat-
ing nystagmus (slow phase to the left ) — results from
injury to the left vestibular nucleus and cerebellar system.
To understand the nystagmus, point your index fi ngers
toward midline to demonstrate the tonic drive that each
side of the medulla places on the eyes. Th en drop your
left hand to indicate a left medullary lesion: the right
side now forces the eyes to the left , which is the slow
phase. Th e direction of the nystagmus, itself, refers to the
fast phase: the right-beating compensatory mechanisms
that respond to the slow phase.
Encircle the aforementioned structures; injury to this
lateral medullary region is called Wallenberg’s syndrome.
Wallenberg’s syndrome most commonly occurs from a
posterior inferior cerebellar artery territory infarct
caused by a branch occlusion of a vertebral artery. As a
fi nal note, through not fully determined pathophysio-
logic mechanisms, hiccups are also commonly encoun-
tered in Wallenberg’s syndrome.^2 , 3 , 5 , 7 , 8 , 18 – 23Case II
Patient presents with dysarthria, right-side weakness,
and sensory disturbance. Exam reveals dysarthric speech;
right hemibody loss of vibration and proprioception
sensation; and right arm and leg weakness. And with
tongue protrusion, there is tongue deviation to the left.
Facial sensation and facial strength is spared.
Show that the dysarthria and tongue deviation result
from injury to the left hypoglossal nucleus; that the right
side large fi ber sensory defi cit is from injury to the left
medial lemniscus tract; and that the right side weakness
is from injury to the left medullary pyramid. Encircle
these structures and label this syndrome as Dejerine’s
syndrome, which results from injury to the medial
medulla.^2 , 3 , 5 , 7 , 8 , 24 – 26