The patient is a college graduate with Lyme encephalopathy (LE). While stopped at a traffic light, she described her thought processes as having a “fog-like” sluggishness. When the light changes, she knows the change from red to green has significance, but at that moment cannot recall that green means go and red means stop.
This is one of many examples of cognitive impairments
associated with Lyme disease. Although some cognitive symptoms are indirectly a
result of other neurological or emotional impairments, others are a direct
result of dysfunction of the cerebral cortex where cognitive processing occurs.
Laboratory tests such as SPECT scans, MRI’s, PET scans, and psychological
testing have demonstrated physiological and anatomical findings associated with
dysfunction of the cerebral cortex in patients with Lyme and tick-borne
diseases. The examination of human and animal brains have further supported
The cognitive impairments from Lyme disease are
very different than we see in Alzheimer’s disease. Lyme disease is predominately
a disease of the white matter, while Alzheimer’s is predominately a disease of
the gray matter. Memory association occurs in the white matter, while memory is
stored in the gray matter. White matter dysfunction is a difficulty with
slowness of recall, and incorrect associations. In contrast, gray matter
dysfunction is a loss of the information which has previously been stored. For
example, and Alzheimer’s patient may not recall the word “pen”, while an LE
patient may have a slowness of recall or retrieval of a closely related word.
Some of the symptoms I will describe are also found in encephalopathies
associated with other illnesses, such as chronic fatigue syndrome, lupus stroke,
AIDS, or other diseases which affect the brain. Although no single sign or
symptom may be diagnostic of Lyme disease in a mental status exam, we instead
look for a cluster and a pattern of signs and symptoms that are commonly
associated with Lyme disease.
Everyone with LE has their own unique
profile of symptoms. The assessment of these signs and symptoms is one facet of
the total clinical assessment of Lyme disease. There are many ways of
categorizing cognitive functioning. Let’s begin with a simple model of
perception, encoding these perceptions into memory, processing what we perceive,
imagery, and finally organizing and planning a response.
functions such as flexing the index finger of the right hand, correlates with a
relatively simple brain circuitry. More complex functions such as flying an
airplane requires the action of a more integrated neural circuitry. The
difference between these two actions is like the difference between playing
middle C on a piano vs. a symphony playing an entire
Many Lyme disease patients have
acquired attention impairments which were not present before the onset of the
disease. There may be difficulty sustaining attention, increased distractibility
when frustrated, and a greater difficulty prioritizing which perceptions are
deserving of a higher allocation of attention.
If we compare attention
span to the lens of a camera, we need the flexibility to constantly shift the
allocation of attention dependency upon the current life situation. For example,
we shift back and forth between a wide angle and a zoom lens focus to increase
or decrease acuity of attention depending on the needs of the current situation.
A loss of this flexibility results in some combination of a loss of acuity
(hypoacusis), and/or excessive acuity to the wrong environmental perceptions
(hyperacusis). Hyperacuity can be auditory (hearing), visual, tactile (touch),
and olfactory (smell).
Auditory hyperacusis is the most common. Sounds
seem louder and more annoying. Sometimes there is selective auditory hyperacusis
to specific types of sounds. Visual hyperacusis may be in response to bright
lights or certain types of artificial lighting. Tactile hyperacusis may be in
response to tight fitting or scratchy clothing, vibrations, temperature and
merely being touched may be painful. Some patients prefer to wear loose fitting
sweat suits and are frustrated that being touched can be painful. Olfactory
hyperacusis may result in an excessive reactivity to certain smells, such as
perfumes, soaps, petroleum products, etc.
the storage and retrieval of information for later use. There are several
different memory deficits associated with LE. Memory is broken down into several
functions – working memory, memory encoding, memory storage and memory
Working memory is a component of executive functioning. An example
of working memory is the ability to spell the word “world” backwards. Sometimes
there are impairments of working memory as it pertains to a working spatial
memory, i.e. forgetting where doors are located or where a car is
Encoding is the placement of a memory into storage. We cannot
retrieve a memory that was not encoded correctly into memory in the first place.
One patient described being upset that someone had eaten yogurt in her kitchen
during the night. Her activity during the night was not encoded into
Short term (recent) memory is the ability to remember information
for relatively brief periods of time. In contrast, long term memory is
information from years in the past (or remote). In LE, there is first a loss of
short term memory followed by a loss of long term memory very late in the
illness. Patients may have slowness of recall with different types of explicit
(or factual) information, such as words, numbers, names, faces or
geographical/spatial cues. Not as common, there may also be slowness of recall
if implicit information, such as tying shoes, or doing other procedural memory
Errors in memory retrieval include errors with letter and/or
number sequences. This can include letter reversals, reversing the sequence of
letters in words, spelling errors, number reversals, or word substitution errors
(inserting the opposite, closely related or wrong words in a
Processing is the creation of
associations which allow us to interpret complex information and to respond in
an adaptive manner. Some LE patients say they feel like they acquired dyslexia
or other learning disabilities, which were not present previously. Examples of
processing functions that may be impaired in the presence of LE include the
Reading comprehension: The ability to understand what is being
Auditory comprehension: The ability to understand spoken
Sound localization: The ability to localize the source of a
Visual spatial perception: Impairments result in spatial
perceptual distortions. One example is microscopia, in which things seem smaller
than they really are. One patient lost depth perception, and had several
accidents when the car in front of her stopped. A problem associated with visual
spatial processing is optic ataxia, in which there is difficulty targeting
movements through space. For example, there may be a tendency to bump into
doorways, difficulty driving and parking a car in tight spaces, and targeting
errors when placing and reaching for objects. One patient with optic ataxia, was
stopped by a policeman while driving two miles to my office because he kept
swerving across the center line. Before Lyme disease he could consistently shoot
13 to 14 out of 15 free throws from the basketball foul line. Now he averages 3
of 15, and misses some shots be several feet.
laterality: The ability to rotate something 180 degrees in your mind. For
example, the ability to copy, rather than mirror, the movements of an aerobics
instructor facing you.
Left-right orientation: The ability to immediately
perceive the difference between left and right. Although this is a part of
congenital Gertsmann’s syndrome or angular gyrus syndrome, acquired left-right
confusion is the result of an encephalopathic process.
ability: The ability to perform mathematical calculations without using fingers
or calculators. Many LE patients describe an increased error rate with their
Fluency of speech: The ability of speech to flow smoothly.
This function is dependent upon adequate speed of word
Stuttering: The tendency to stutter when speech is begun with
Slurred speech: A slurring of words, which can give the
appearance of intoxication.
Fluency of written language: The ability to
express thoughts into writing.
Handwriting: The ability to write words
and sentences clearly.
Imagery is a uniquely human trait. It
is the ability to create what never was within our minds. When functioning
properly, it is a component of human creativity, but when impaired, it can
result in psychosis. Imagery functions that can be affected by LE
Capacity for visual imagery: The ability to picture something,
such as a map, in our head.
Intrusive images: Images that suddenly appear
which may be aggressive, horrific, sexual or otherwise.
hallucinations: The continuation of a dream, even after being fully
Vivid nightmares: A tendency towards nightmares of a vivid
Illusions: Auditory, visual, tactile and/or olfactory
perceptions which are distorted or misperceived.
seeing, feeling and/or smelling something that is not present. In LE, sometimes
this takes the form of hearing music or a radio station in the background.
Unlike schizophrenic hallucinations, these are accompanied by a clear sensorium,
and the patient is aware hallucinations are present.
loss of a sense of physical existence.
Derealization: A loss of a sense
that the environment is real.
Organizing and Planning
planning a response is the most complex mental function, and is dependent upon
all the functions already described. These functions, along with attention span
and working memory, are referred to as executive functioning. Organizing and
planning functions that can be
affected by LE include:
The ability to focus thought and maintain mental tracking while performing
problem solving tasks.
“Brain fog”: Described by many LE patients.
Although difficult to describe in objective, scientific terms: it is best
described as a slowness, weakness, and inaccuracy of thought processes.
Prioritizing, organizing, and implementing multiple tasks with effective time
Simultasking: The ability to concentrate and be effective
while performing multiple simultaneous tasks.
Initiative: The ability to
initiate spontaneous thoughts, ideas and actions rather than being apathetic or
merely responding to environmental cues.
Abstract reasoning: The capacity
for complex problem solving.
Obsessive thoughts: May interfere with
Racing thoughts: May interfere with productive
An assessment of each of these areas of functioning is a
critical component in the clinical assessment of LE. The cognitive assessment is
only a part of the assessment of LE. Other components include the psychiatric
assessment, the neurological assessment, a review of somatic symptoms,
epidemiological considerations and laboratory testing when indicated. I have
gradually developed a structured cognitive assessment which focuses upon the
areas mentioned after examining many patients with late stage neuropsychiatric